Add SecurityTokenClaimsIdentity

[pmaytak]

#2531

Performance results: #2858 (comment)

[pmaytak]

BenchmarkDotNet v0.13.12, Windows 11 (10.0.26100.2033) (Hyper-V)
Intel Xeon Platinum 8370C CPU 2.80GHz, 1 CPU, 16 logical and 8 physical cores
.NET SDK 8.0.403
[Host] : .NET 8.0.10 (8.0.1024.46610), X64 RyuJIT AVX-512F+CD+BW+DQ+VL+VBMI
MediumRun : .NET 8.0.10 (8.0.1024.46610), X64 RyuJIT AVX-512F+CD+BW+DQ+VL+VBMI

Job=MediumRun MaxAbsoluteError=10.0000 ms IterationCount=15
LaunchCount=4 WarmupCount=10

Method	Mean	Error	StdDev	P90	P95	P100	Ratio	Gen0	Allocated	Alloc Ratio
ClaimsIdentity_FindAll	265.57 ns	0.732 ns	1.591 ns	267.64 ns	268.29 ns	269.61 ns	1.00	0.0110	280 B	1.00
NewClaimsIdentity_FindAll	261.72 ns	0.813 ns	1.766 ns	264.42 ns	264.73 ns	265.06 ns	0.99	0.0119	304 B	1.09
ClaimsIdentity_FindFirst	153.93 ns	0.744 ns	1.664 ns	155.76 ns	155.96 ns	156.54 ns	1.00	0.0050	128 B	1.00
NewClaimsIdentity_FindFirst	50.06 ns	0.670 ns	1.498 ns	51.71 ns	51.88 ns	51.99 ns	0.33	0.0032	80 B	0.62
ClaimsIdentity_HasClaim	168.23 ns	0.437 ns	0.951 ns	169.63 ns	169.88 ns	170.89 ns	1.00	0.0052	136 B	1.00
NewClaimsIdentity_HasClaim	58.17 ns	0.585 ns	1.260 ns	59.48 ns	59.64 ns	59.86 ns	0.35	0.0031	80 B	0.59

[brentschmaltz]

This naming makes sense for JWT, but not for SAML

[pmaytak]

The naming is sort of temporary for now. We have similarly named methods that perform old logic; so tried to make these stand out for the ease of refactoring for now.