Fix MA0194 merge with existing and-patterns

[meziantou]

Why

MA0194 did not merge some valid is expressions when one side already used a relational and pattern. It could also produce ambiguous output without explicit grouping when or combined with an and subpattern.

What changed

• Reused existing pattern syntax in TryCreatePatternSyntax when Roslyn already provides a PatternSyntax, so relational patterns remain mergeable.
• Updated parenthesizing logic to add parentheses for mixed precedence in both directions (and with or, and or with and).
• Added a regression test (LogicalOr_ParenthesizeAndPattern) to verify:
  • marker is 0x01 || marker is >= 0xD0 and <= 0xD7
  • becomes marker is 0x01 or (>= 0xD0 and <= 0xD7).

Validation

• dotnet test tests/Meziantou.Analyzer.Test/Meziantou.Analyzer.Test.csproj --filter "FullyQualifiedName~MergeIsPatternChecksAnalyzerTests" --nologo