Suite-granularity test sharding reliably covers every module

tuist test suite-granularity sharding no longer silently drops entire test modules. Plans were previously built by scraping streamed stdout from xcodebuild -enumerate-tests, which could truncate or interleave on large bundles (observed missing 25 of 69 targets on the same commit). The CLI now reads machine-parseable JSON enumeration output and verifies every module in the .xctestrun universe is present, so all scheduled tests actually run. If a module genuinely cannot be enumerated, the command now fails with a clear error instead of returning an incomplete plan.