Reduce per-lookup overhead from key validation in HybridCache

[MihaZupan]

IndexOfAny(char[]) has per-call overhead to figure out what to do.
On modern .NET it would eventually hit a vectorized helper, but has to analyze the values every time.

Quick test with a default MemoryCache:

.NET 9/10

Method	Job	KeyLength	Mean	Error	Ratio
GetCachedValue	main	1	41.35 ns	0.650 ns	1.00
GetCachedValue	pr	1	41.71 ns	0.824 ns	1.01
GetCachedValue	main	16	59.67 ns	1.192 ns	1.00
GetCachedValue	pr	16	41.36 ns	0.852 ns	0.69
GetCachedValue	main	100	70.41 ns	1.420 ns	1.00
GetCachedValue	pr	100	53.16 ns	1.043 ns	0.76

Framework

Method	Job	KeyLength	Mean	Error	Ratio
GetCachedValue	main	1	179.1 ns	3.57 ns	1.00
GetCachedValue	pr	1	120.2 ns	2.36 ns	0.67
GetCachedValue	main	16	187.5 ns	3.55 ns	1.00
GetCachedValue	pr	16	136.2 ns	2.70 ns	0.73
GetCachedValue	main	100	296.6 ns	5.82 ns	1.00
GetCachedValue	pr	100	208.1 ns	4.07 ns	0.70

Microsoft Reviewers: Open in CodeFlow

[mgravell]

Nice tip!