Windows cross builds execute tests on the Windows host through windows_test_launcher, while windows_unittest uses static remote linking. The native MSVC toolchain now respects debug_symbols in every compilation mode, and gather_failed_tests.py downloads PDB/debug files without changing the saved build configuration or discarding an explicit download regex.

First of the two remaining extractions from #63670. Cross compilation remains opt-in here; the rollout and documentation change will be stacked on this PR. Epic: DEVPROD-33617.