Merging internal commits for release/8.0

[vseanreesermsft]

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[Copilot]

Pull request overview

This PR merges internal release/8.0 changes into the COSE implementation, primarily improving decode behavior for indefinite-length CBOR structures and tightening critical header validation, with accompanying test coverage.

Changes:

• Update COSE header map decoding to support indefinite-length CBOR maps and improve error surfacing for well-known header validation failures.
• Update critical headers handling to properly process indefinite-length arrays and reject empty crit arrays.
• Add decode tests for critical header error cases across Sign1 and MultiSign, including detached/attached and definite/indefinite encodings.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
src/libraries/System.Security.Cryptography.Cose/tests/CoseMessageTests.Sign.CustomHeaderMaps.cs	Expands signing tests to cover definite vs indefinite critical header encodings (but currently has invalid argument ordering at call sites).
src/libraries/System.Security.Cryptography.Cose/tests/CoseMessageTests.DecodeSign1.cs	Adds decode tests validating exceptions for missing/empty/invalid critical headers across encoding variants.
src/libraries/System.Security.Cryptography.Cose/tests/CoseMessageTests.DecodeMultiSign.cs	Adds decode tests validating exceptions for missing/empty/invalid critical headers across encoding variants.
src/libraries/System.Security.Cryptography.Cose/src/System/Security/Cryptography/Cose/CoseMessage.cs	Updates header bucket decoding to handle indefinite-length maps; improves critical header parsing and exception behavior.
src/libraries/System.Security.Cryptography.Cose/src/System.Security.Cryptography.Cose.csproj	Bumps servicing version and changes package generation behavior on build.