[CLEAN] Synthetic Benchmark PR #61305 - Search for slnx files when setting solution-relative content root

[bar-qodo]

Benchmark PR dotnet#61305

Type: Clean (correct implementation)

Original PR Title: Search for slnx files when setting solution-relative content root
Original PR Description: Search for slnx files when setting solution-relative content root

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Fixes dotnet#61304

Original PR URL: dotnet#61305