Add missing cases to UseProperAssertMethod analyzer

[Evangelink]

No description provided.

[Copilot]

Pull request overview

This PR extends the UseProperAssertMethodsAnalyzer to recognize two additional patterns that were previously missed:

1. Reversed null comparisons where null is the left operand (e.g., null == x instead of x == null)
2. Mixed numeric type comparisons (e.g., int > long)

Changes:

• Removed TODO comments indicating these cases were not yet implemented
• Enhanced null comparison detection to check both left and right operands for null literals
• Added comprehensive test coverage for the newly supported patterns

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/Analyzers/MSTest.Analyzers/UseProperAssertMethodsAnalyzer.cs	Enhanced IsEqualsNullBinaryOperator and IsNotEqualsNullBinaryOperator to check both operands for null, enabling detection of reversed null comparisons
test/UnitTests/MSTest.Analyzers.UnitTests/UseProperAssertMethodsAnalyzerTests.cs	Added WhenAssertUsesReversedNullComparisons test to verify all reversed null comparison scenarios and WhenAssertIsTrueWithMixedNumericComparison test for mixed numeric types