Normalize percent-encoding hex case in SHR p-claim validation

[debchoudhury-id4s]

Summary

• normalize ASCII hexadecimal letter casing inside valid %XX triplets during Signed HTTP Request p claim validation
• preserve literal path-case behavior through UseCaseSensitivePClaimComparison, slash tolerance, encoded delimiters, and unchanged p claim creation output
• add validation and creation compatibility coverage and document the validation-only change

Testing

• dotnet clean Wilson.sln -c Debug
• dotnet build Wilson.sln -c Debug (0 warnings, 0 errors)
• dotnet test Wilson.sln -c Debug --no-build (21,813 passed, 8 skipped, 0 failed across net6.0/net8.0/net9.0/net10.0)
• focused PClaim tests passed on net6.0, net8.0, net9.0, and net10.0
• net462/net472 builds succeeded locally, but test execution requires the repository strong-name bypass configured in CI

Work item: https://identitydivision.visualstudio.com/Engineering/_workitems/edit/3699975/
AB#3699975

[debchoudhury-id4s]

Superseded by #3561, which uses an AzureAD-owned source branch consistent with this repository's PR strategy.