nopool

[bitfaster]

Remove use of array pooling, approx 12% better throughput. Now very close to 6 million ops/sec.

Method	Runtime	Mean	Error	StdDev	Ratio	Allocated
ConcurrentDictionary	.NET 6.0	7.362 ns	0.0334 ns	0.0297 ns	1.00	-
ConcurrentLfuBackground	.NET 6.0	36.728 ns	0.9014 ns	2.6436 ns	4.82	-
ConcurrentLfuForeround	.NET 6.0	67.891 ns	0.3150 ns	0.2947 ns	9.23	-
ConcurrentLfuThreadPool	.NET 6.0	53.836 ns	0.7426 ns	0.6946 ns	7.31	-
ConcurrentLfuNull	.NET 6.0	27.233 ns	0.0743 ns	0.0695 ns	3.70	-
ConcurrentDictionary	.NET Framework 4.8	13.889 ns	0.1314 ns	0.1026 ns	1.00	-
ConcurrentLfuBackground	.NET Framework 4.8	64.676 ns	1.3003 ns	1.8229 ns	4.64	-
ConcurrentLfuForeround	.NET Framework 4.8	78.924 ns	0.7792 ns	0.7288 ns	5.69	-
ConcurrentLfuThreadPool	.NET Framework 4.8	44.644 ns	0.9221 ns	1.5407 ns	3.24	-
ConcurrentLfuNull	.NET Framework 4.8	37.809 ns	0.0954 ns	0.0846 ns	2.72	-