Rewrote the Windows presubmit script from .ps1 to .bat to fix execution issues on Kokoro Windows executors where .ps1 files could not be executed directly. Updated the build config to point to the new batch file.

Rewrote the Windows presubmit script from .ps1 to .bat to fix execution issues on Kokoro Windows executors where .ps1 files could not be executed directly. Updated the build config to point to the new batch file. #87