Convert TLru policy to use Duration

[bitfaster]

Need to verify whether this has regressed perf. Bench run below showed FastConcurrentTLru is slower than FastConcLruAfterAccess, which was not previously the case. But overall numbers are higher than when I last ran, need to repeat on a clean state.

Method	Runtime	Mean	Error	StdDev	Ratio	Code Size	Allocated
ConcurrentDictionary	.NET 6.0	7.291 ns	0.0439 ns	0.0389 ns	1.00	1,523 B	-
FastConcurrentLru	.NET 6.0	8.399 ns	0.1118 ns	0.1046 ns	1.15	7,047 B	-
ConcurrentLru	.NET 6.0	14.659 ns	0.0586 ns	0.0520 ns	2.01	7,294 B	-
AtomicFastLru	.NET 6.0	19.814 ns	0.0420 ns	0.0393 ns	2.72	NA	-
FastConcurrentTLru	.NET 6.0	11.609 ns	0.0224 ns	0.0209 ns	1.59	7,190 B	-
FastConcLruAfterAccess	.NET 6.0	11.232 ns	0.0493 ns	0.0385 ns	1.54	6,342 B	-
FastConcLruAfter	.NET 6.0	13.695 ns	0.1964 ns	0.1837 ns	1.88	7,683 B	-
ConcurrentTLru	.NET 6.0	16.209 ns	0.0257 ns	0.0228 ns	2.22	7,705 B	-
ConcurrentLfu	.NET 6.0	30.495 ns	1.1803 ns	3.4803 ns	4.28	NA	-
ClassicLru	.NET 6.0	43.279 ns	0.0622 ns	0.0486 ns	5.94	NA	-
RuntimeMemoryCacheGet	.NET 6.0	110.979 ns	0.3277 ns	0.3065 ns	15.22	49 B	32 B
ExtensionsMemoryCacheGet	.NET 6.0	50.261 ns	0.9936 ns	1.0632 ns	6.87	78 B	24 B
ConcurrentDictionary	.NET Framework 4.8	13.515 ns	0.0456 ns	0.0427 ns	1.00	4,127 B	-
FastConcurrentLru	.NET Framework 4.8	15.121 ns	0.0663 ns	0.0620 ns	1.12	27,372 B	-
ConcurrentLru	.NET Framework 4.8	19.176 ns	0.2836 ns	0.2514 ns	1.42	27,676 B	-
AtomicFastLru	.NET Framework 4.8	30.766 ns	0.0454 ns	0.0403 ns	2.28	358 B	-
FastConcurrentTLru	.NET Framework 4.8	48.792 ns	0.1256 ns	0.1175 ns	3.61	27,664 B	-
FastConcLruAfterAccess	.NET Framework 4.8	45.270 ns	0.0731 ns	0.0648 ns	3.35	358 B	-
FastConcLruAfter	.NET Framework 4.8	46.741 ns	0.0260 ns	0.0203 ns	3.46	358 B	-
ConcurrentTLru	.NET Framework 4.8	47.776 ns	0.0980 ns	0.0869 ns	3.53	28,016 B	-
ConcurrentLfu	.NET Framework 4.8	56.767 ns	0.5338 ns	0.4994 ns	4.20	NA	-
ClassicLru	.NET Framework 4.8	55.115 ns	0.1339 ns	0.1187 ns	4.08	NA	-
RuntimeMemoryCacheGet	.NET Framework 4.8	285.584 ns	1.2160 ns	1.0780 ns	21.13	33 B	32 B
ExtensionsMemoryCacheGet	.NET Framework 4.8	91.806 ns	1.8453 ns	1.9745 ns	6.77	82 B	24 B

[coveralls]

coverage: 98.661% (+0.001%) from 98.66%
when pulling 4a2096c on users/alexpeck/tlruduration
into 56f9f24 on main.

[bitfaster]

Cleaner run:

Method	Runtime	Mean	Error	StdDev	Ratio	Code Size	Allocated
ConcurrentDictionary	.NET 6.0	7.624 ns	0.0807 ns	0.0674 ns	1.00	1,523 B	-
FastConcurrentLru	.NET 6.0	8.746 ns	0.0453 ns	0.0424 ns	1.15	4,437 B	-
ConcurrentLru	.NET 6.0	16.628 ns	0.1459 ns	0.1364 ns	2.18	4,684 B	-
FastConcurrentTLru	.NET 6.0	11.568 ns	0.0502 ns	0.0419 ns	1.52	4,580 B	-
FastConcLruAfterAccess	.NET 6.0	11.842 ns	0.0899 ns	0.0797 ns	1.55	5,256 B	-
FastConcLruAfter	.NET 6.0	13.227 ns	0.0509 ns	0.0398 ns	1.74	5,073 B	-
ConcurrentTLru	.NET 6.0	16.156 ns	0.0528 ns	0.0440 ns	2.12	5,095 B	-
ConcurrentDictionary	.NET Framework 4.8	14.865 ns	0.0886 ns	0.0785 ns	1.00	4,127 B	-
FastConcurrentLru	.NET Framework 4.8	15.880 ns	0.0892 ns	0.0790 ns	1.07	27,372 B	-
ConcurrentLru	.NET Framework 4.8	19.217 ns	0.1467 ns	0.1372 ns	1.29	27,676 B	-
FastConcurrentTLru	.NET Framework 4.8	46.152 ns	0.1685 ns	0.1407 ns	3.10	27,664 B	-
FastConcLruAfterAccess	.NET Framework 4.8	45.317 ns	0.1274 ns	0.1129 ns	3.05	358 B	-
FastConcLruAfter	.NET Framework 4.8	46.978 ns	0.2021 ns	0.1890 ns	3.16	358 B	-
ConcurrentTLru	.NET Framework 4.8	48.268 ns	0.8492 ns	0.7091 ns	3.25	28,016 B	-

Comparable to results here #438

Method	Runtime	Mean	Error	StdDev	Ratio	Code Size	Allocated
ConcurrentDictionary	.NET 6.0	7.316 ns	0.1773 ns	0.2111 ns	1.00	1,523 B	-
FastConcurrentLru	.NET 6.0	9.257 ns	0.2104 ns	0.2583 ns	1.27	7,235 B	-
ConcurrentLru	.NET 6.0	15.503 ns	0.3292 ns	0.3522 ns	2.12	7,482 B	-
FastConcurrentTLru	.NET 6.0	11.973 ns	0.1564 ns	0.1387 ns	1.63	6,394 B	-
ConcurrentTLru	.NET 6.0	16.881 ns	0.3086 ns	0.2577 ns	2.31	7,912 B	-
ConcurrentDictionary	.NET Framework 4.8	14.423 ns	0.3010 ns	0.3091 ns	1.00	4,127 B	-
FastConcurrentLru	.NET Framework 4.8	15.579 ns	0.3166 ns	0.2962 ns	1.08	23,882 B	-
ConcurrentLru	.NET Framework 4.8	21.279 ns	0.3536 ns	0.3307 ns	1.48	24,186 B	-
FastConcurrentTLru	.NET Framework 4.8	48.056 ns	0.8575 ns	0.9875 ns	3.33	24,154 B	-
ConcurrentTLru	.NET Framework 4.8	49.802 ns	0.5524 ns	0.4897 ns	3.46	24,506 B	-