feat(git): Use local git for conflict detection (#12575)

lib/platform/azure/__snapshots__/util.spec.ts.snap

lib/platform/azure/util.spec.ts

lib/platform/azure/util.ts

...latform/bitbucket-server/__snapshots__/index.spec.ts.snap

lib/platform/bitbucket-server/index.ts

lib/platform/bitbucket/__snapshots__/index.spec.ts.snap

lib/platform/bitbucket/index.spec.ts

lib/platform/bitbucket/index.ts

lib/platform/bitbucket/utils.spec.ts

lib/platform/bitbucket/utils.ts

lib/platform/gitea/__snapshots__/index.spec.ts.snap

lib/platform/gitea/index.ts

lib/platform/github/__snapshots__/index.spec.ts.snap

lib/platform/github/index.ts

lib/platform/gitlab/__snapshots__/index.spec.ts.snap

lib/platform/gitlab/index.ts

lib/platform/types.ts

lib/util/git/index.spec.ts

lib/util/git/index.ts

lib/workers/branch/index.ts