Re-land the Windows git pre-push check patch with proper communication of changes

[mtolmacs]

Re-land the patches which re-enable full Windows git pre-push support, but this time with more conservative communication and assumptions.

Issues fixed by this PR

• flutter/flutter#108122
• flutter/flutter#107920
• flutter/flutter#86506
• flutter/flutter#106615

flutter/tests repo impact

None.

Pre-launch Checklist

• [x] I read the Contributor Guide and followed the process outlined there for submitting PRs.
• [x] I read the Tree Hygiene wiki page, which explains my responsibilities.
• [x] I read and followed the Flutter Style Guide and the C++, Objective-C, Java style guides.
• [x] I listed at least one issue that this PR fixes in the description above.
• [ ] I added new tests to check the change I am making or feature I am adding, or Hixie said the PR is test-exempt. See testing the engine for instructions on writing and running engine tests.
• [x] I updated/added relevant documentation (doc comments with ///).
• [x] I signed the CLA.
• [ ] All existing and new tests are passing.

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