Modernize linting and test infrastructure

[TheFellow]

Summary

• add cedar-style formatting, analyzer, warning-as-error, and CI gates
• pin the .NET 10 LTS SDK and update the test project from .NET 5 / MSTest 1 to .NET 10 / MSTest 4
• apply formatter and analyzer fixes, including correct null equality and empty-group behavior
• repair NuGet packaging and document where records supersede this library versus where its ordered/unordered collection semantics remain useful

Validation

• dotnet format ValueTypes/ValueTypes.sln --verify-no-changes --no-restore
• dotnet build ValueTypes/ValueTypes.sln --configuration Release --no-restore (0 warnings, 0 errors)
• dotnet test ValueTypes/ValueTypes.sln --configuration Release --no-build (399 passed)
• dotnet pack ValueTypes/ValueTypes/ValueTypes.csproj --configuration Release --no-build