Introduce object pooling

[lahma]

This PR introduces object pooling for top memory pressure creators:

• Reference
• Completion
• ArgumentsInstance

With this change they practically disappear from performance report. The approach is opportunistic/best effort. When we are in code path that no longer needs the deep-acquire object we release it, unfortunately using pattern cannot be used.

Esprima.Benchmark.DromaeoBenchmark

Diff	Method	FileName	Mean	Gen 0	Gen 1	Gen 2	Allocated
Old	Run	dromaeo-3d-cube	107.09 ms	7437.5000	250.0000	-	31.67 MB
New			107.96 ms (+1%)	1312.5000 (-82%)	250.0000 (0%)	-	7107.59 KB (-78%)
Old	Run	dromaeo-core-eval	25.92 ms	1718.7500	-	-	6.9 MB
New			24.98 ms (-4%)	62.5000 (-96%)	-	-	298.95 KB (-96%)
Old	Run	dromaeo-object-array	270.44 ms	45125.0000	2062.5000	1000.0000	186.35 MB
New			262.77 ms (-3%)	39500.0000 (-12%)	2000.0000 (-3%)	1000.0000 (0%)	166027.07 KB (-11%)
Old	Run	dromaeo-object-regexp	1,168.48 ms	71812.5000	35312.5000	22250.0000	479.86 MB
New			1,141.61 ms (-2%)	57562.5000 (-20%)	35062.5000 (-1%)	22000.0000 (-1%)	434680.59 KB (-9%)
Old	Run	dromaeo-object-string	1,584.29 ms	249500.0000	183437.5000	179187.5000	1457.82 MB
New			1,524.09 ms (-4%)	226687.5000 (-9%)	184625.0000 (+1%)	181687.5000 (+1%)	1393645.01 KB (-4%)
Old	Run	dromaeo-string-base64	236.82 ms	16062.5000	375.0000	-	65.37 MB
New			236.61 ms (0%)	6187.5000 (-61%)	187.5000 (-50%)	-	26458.12 KB (-60%)

Esprima.Benchmark.SunSpiderBenchmark

Diff	Method	FileName	Mean	Gen 0	Gen 1	Gen 2	Allocated
Old	Run	3d-cube	848.7 ms	63687.5000	312.5000	62.5000	256.97 MB
New			826.2 ms (-3%)	10250.0000 (-84%)	312.5000 (0%)	62.5000 (0%)	42.9 MB (-83%)
Old	Run	3d-morph	796.1 ms	41937.5000	5875.0000	1812.5000	193.86 MB
New			759.8 ms (-5%)	10875.0000 (-74%)	2312.5000 (-61%)	1000.0000 (-45%)	61.05 MB (-69%)
Old	Run	3d-raytrace	648.6 ms	53562.5000	1000.0000	125.0000	216.57 MB
New			648.5 ms (0%)	21937.5000 (-59%)	500.0000 (-50%)	62.5000 (-50%)	90.1 MB (-58%)
Old	Run	access-binary-trees	260.5 ms	36125.0000	437.5000	-	145.24 MB
New			259.5 ms (0%)	19187.5000 (-47%)	250.0000 (-43%)	-	77.08 MB (-47%)
Old	Run	access-fannkuch	2,707.8 ms	172437.5000	250.0000	-	689.76 MB
New			2,656.7 ms (-2%)	7062.5000 (-96%)	250.0000 (0%)	-	28.43 MB (-96%)
Old	Run	access-nbody	764.4 ms	57500.0000	62.5000	-	230.06 MB
New			745.0 ms (-3%)	10625.0000 (-82%)	62.5000 (0%)	-	42.73 MB (-81%)
Old	Run	access-nsieve	980.3 ms	62937.5000	7937.5000	2937.5000	260.87 MB
New			948.8 ms (-3%)	12812.5000 (-80%)	3875.0000 (-51%)	1812.5000 (-38%)	62.71 MB (-76%)
Old	Run	bitops-3bit-bits-in-byte	560.9 ms	54937.5000	-	-	219.81 MB
New			544.9 ms (-3%)	20687.5000 (-62%)	-	-	82.99 MB (-62%)
Old	Run	bitops-bits-in-byte	965.9 ms	80625.0000	62.5000	-	322.7 MB
New			947.1 ms (-2%)	13437.5000 (-83%)	62.5000 (0%)	-	53.98 MB (-83%)
Old	Run	bitops-bitwise-and	653.2 ms	45625.0000	62.5000	-	182.65 MB
New			600.7 ms (-8%)	10125.0000 (-78%)	-	-	40.74 MB (-78%)
Old	Run	bitops-nsieve-bits	1,047.0 ms	66750.0000	4375.0000	375.0000	269.04 MB
New			1,010.6 ms (-3%)	17250.0000 (-74%)	250.0000 (-94%)	62.5000 (-83%)	71.02 MB (-74%)
Old	Run	controlflow-recursive	357.1 ms	55687.5000	-	-	222.91 MB
New			358.6 ms (0%)	29062.5000 (-48%)	62.5000	-	116.32 MB (-48%)
Old	Run	crypto-aes	643.3 ms	44250.0000	312.5000	62.5000	179.2 MB
New			645.4 ms (0%)	5250.0000 (-88%)	250.0000 (-20%)	-	23.11 MB (-87%)
Old	Run	crypto-md5	421.5 ms	51250.0000	312.5000	62.5000	207.1 MB
New			409.2 ms (-3%)	30187.5000 (-41%)	312.5000 (0%)	62.5000 (0%)	123.04 MB (-41%)
Old	Run	crypto-sha1	417.5 ms	47687.5000	312.5000	62.5000	192.39 MB
New			404.7 ms (-3%)	24875.0000 (-48%)	187.5000 (-40%)	-	101.27 MB (-47%)
Old	Run	date-format-tofte	433.6 ms	36062.5000	-	-	144.36 MB
New			425.1 ms (-2%)	12187.5000 (-66%)	62.5000	-	49.05 MB (-66%)
Old	Run	date-format-xparb	373.4 ms	18062.5000	250.0000	-	72.86 MB
New			372.6 ms (0%)	10750.0000 (-40%)	250.0000 (0%)	-	43.57 MB (-40%)
Old	Run	math-cordic	1,253.7 ms	110000.0000	125.0000	-	440.03 MB
New			1,220.4 ms (-3%)	21562.5000 (-80%)	62.5000 (-50%)	-	86.4 MB (-80%)
Old	Run	math-partial-sums	401.5 ms	26812.5000	-	-	107.29 MB
New			390.7 ms (-3%)	6500.0000 (-76%)	-	-	26.15 MB (-76%)
Old	Run	math-spectral-norm	475.1 ms	48312.5000	-	-	193.43 MB
New			458.3 ms (-4%)	19187.5000 (-60%)	-	-	76.96 MB (-60%)
Old	Run	regexp-dna	343.3 ms	2000.0000	1687.5000	1375.0000	13.46 MB
New			343.7 ms (0%)	2250.0000 (+13%)	1937.5000 (+15%)	1562.5000 (+14%)	13.45 MB (0%)
Old	Run	string-base64	350.1 ms	23812.5000	250.0000	-	96.61 MB
New			351.1 ms (0%)	8812.5000 (-63%)	437.5000 (+75%)	-	36.92 MB (-62%)
Old	Run	string-fasta	601.0 ms	57875.0000	-	-	231.69 MB
New			596.6 ms (-1%)	25625.0000 (-56%)	-	-	102.6 MB (-56%)
Old	Run	string-tagcloud	257.0 ms	26187.5000	2125.0000	750.0000	113.18 MB
New			250.7 ms (-2%)	14875.0000 (-43%)	1687.5000 (-21%)	625.0000 (-17%)	68.05 MB (-40%)
Old	Run	string-unpack-code	202.0 ms	27187.5000	6250.0000	1375.0000	118.12 MB
New			197.2 ms (-2%)	14625.0000 (-46%)	4625.0000 (-26%)	1187.5000 (-14%)	70.22 MB (-41%)
Old	Run	string-validate-input	241.7 ms	20375.0000	375.0000	62.5000	84.8 MB
New			236.3 ms (-2%)	7500.0000 (-63%)	250.0000 (-33%)	62.5000 (0%)	35.24 MB (-58%)

Jint.Benchmark.ArrayBenchmark

Diff	Method	N	Mean	Gen 0	Allocated
Old	Slice	100	672.9 us	149.4141	615.63 KB
New			685.5 us (+2%)	145.5078 (-3%)	598.44 KB (-3%)
Old	Concat	100	827.7 us	166.0156	683.59 KB
New			791.7 us (-4%)	162.1094 (-2%)	666.41 KB (-3%)
Old	Unshift	100	30,986.7 us	3687.5000	15212.5 KB
New			31,235.1 us (+1%)	3031.2500 (-18%)	12525.78 KB (-18%)
Old	Push	100	17,942.8 us	1406.2500	5846.09 KB
New			18,001.2 us (0%)	593.7500 (-58%)	2518.75 KB (-57%)
Old	Index	100	16,693.3 us	1250.0000	5171.09 KB
New			16,898.0 us (+1%)	343.7500 (-73%)	1515.63 KB (-71%)
Old	Map	100	4,334.2 us	1437.5000	5903.13 KB
New			4,324.5 us (0%)	796.8750 (-45%)	3286.72 KB (-44%)
Old	Apply	100	942.3 us	183.5938	752.34 KB
New			960.3 us (+2%)	176.7578 (-4%)	727.34 KB (-3%)
Old	JsonStringifyParse	100	5,271.2 us	1250.0000	5140.63 KB
New			5,371.5 us (+2%)	1242.1875 (-1%)	5111.72 KB (-1%)

Jint.Benchmark.ArrayStressBenchmark

Diff	Method	N	Mean	Gen 0	Gen 1	Allocated
Old	Jint	20	1.706 s	92437.5000	12562.5000	385.91 MB
New			1.643 s (-4%)	60000.0000 (-35%)	5000.0000 (-60%)	249.81 MB (-35%)

Jint.Benchmark.EvaluationBenchmark

Diff	Method	N	Mean	Gen 0	Allocated
Old	Jint	20	765.5 us	134.7656	554.69 KB
New			743.9 us (-3%)	120.1172 (-11%)	495.16 KB (-11%)

Jint.Benchmark.LinqJsBenchmark

Diff	Method	N	Mean	Gen 0	Gen 1	Gen 2	Allocated
Old	Jint	10	76.41 ms	5187.5000	2500.0000	187.5000	30.71 MB
New			71.07 ms (-7%)	5062.5000 (-2%)	2500.0000 (0%)	-	30.47 MB (-1%)

Jint.Benchmark.MinimalScriptBenchmark

Diff	Method	N	Mean	Gen 0	Allocated
Old	Jint	10	23.65 us	8.5144	34.92 KB
New			22.37 us (-5%)	8.2092 (-4%)	33.67 KB (-4%)

Jint.Benchmark.StopwatchBenchmark

Diff	Method	N	Mean	Gen 0	Gen 1	Allocated
Old	Jint	1	1.598 s	118562.5000	125.0000	474.43 MB
New			1.535 s (-4%)	18875.0000 (-84%)	125.0000 (0%)	75.75 MB (-84%)

Jint.Benchmark.UncacheableExpressionsBenchmark

Diff	Method	N	Mean	Gen 0	Gen 1	Allocated
Old	Benchmark	500	481.7 ms	94187.5000	250.0000	377.11 MB
New			475.6 ms (-1%)	52812.5000 (-44%)	62.5000 (-75%)	211.35 MB (-44%)