gitmodules: Restore but rename upstream .gitmodules

Rename .gitmodules to .gitmodules.unused since our tools/servers don't
support .gitmodules from external projects. Also restore the entries we
removed before. Hopefully this will produce fewer merge conflicts while
still allowing us to replace the needed submodlues with symlinks to
other projects in our manifest.

Bug: 230374325
Change-Id: I833c0c4ad407471ea331ca0b21b6a6f9a5d4535d
1 file changed