Restore full git history for checkouts (#4595)

Restores full git history for checkouts, that allows build-id script to
get number of commits.
This is restored from Cobalt actions code behavior, and should not have
significant impact on build speeds, as we don't work with full Chromium
repo.

b/377927950
b/378163424

.github/workflows/main.yaml

@@ -157,6 +157,8 @@ jobs:
         if: ${{ ! (startsWith(matrix.platform, 'android') && matrix.config == 'debug') }}
         with:
           path: src
+          # Use fetch depth of 0 to get full history for a valid build id.
+          fetch-depth: 0
       - name: Build Cobalt
         uses: ./src/.github/actions/build
         # TODO(bug?): android debug builds are broken.