[STJ] Fix formatting of flag enums when values are overlapping.

[eiriktsarpalis]

Fix #114770.

[Copilot]

Pull Request Overview

This PR fixes the formatting of flag enums when values are overlapping by implementing a topological sort to ensure proper ordering of enum values during serialization. The issue occurs when flag enums have values that are supersets of other values (e.g., BITS01 = 3 which combines BIT0 = 1 and BIT1 = 2).

Key Changes:

• Added topological sorting for flag enums to ensure superset values are processed before their constituent parts
• Implemented Kahn's algorithm to handle the ordering dependencies between overlapping enum values
• Added comprehensive tests to verify the fix works for different scenarios of overlapping flag enum values

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
EnumConverter.cs	Implements topological sorting logic using Kahn's algorithm for flag enums to ensure proper ordering of overlapping values
EnumConverterTests.cs	Adds test cases for flag enums with overlapping bit values to verify serialization produces expected output

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[eiriktsarpalis]

/ba-g test failures unrelated to change.

[eiriktsarpalis]

/backport to release/9.0-staging

[github-actions]

Started backporting to release/9.0-staging: https://github.com/dotnet/runtime/actions/runs/16368520024