refactor: make git package handle all git operations (#38543)

before: gitrepo vs git packages
after: git package fully handle all git operations

by the way, use `WithRepo(repo)` instead of `WithDir(repo.Path)` to hide
path details.

benefits:

1. remove all unnecessary wrappers, developers no need to struggle with
"which package should be used"
2. simplify code, RepositoryFacade can (will) be used everywhere, all
"path" details are (will be) hidden

tests/integration/pull_review_test.go

@@ -18,7 +18,6 @@ import (
 	"gitea.dev/models/unittest"
 	user_model "gitea.dev/models/user"
 	"gitea.dev/modules/git"
-	"gitea.dev/modules/gitrepo"
 	"gitea.dev/modules/test"
 	issue_service "gitea.dev/services/issue"
 	repo_service "gitea.dev/services/repository"
@@ -100,7 +99,7 @@ func TestPullView_CodeOwner(t *testing.T) {
 
 			// capture the current PR head ref so we can wait for the async
 			// refs/pull/N/head sync triggered by the next push to complete
-			baseGitRepo, err := gitrepo.OpenRepository(repo)
+			baseGitRepo, err := git.OpenRepository(repo)
 			require.NoError(t, err)
 			defer baseGitRepo.Close()
 			headRefBefore, err := baseGitRepo.GetRefCommitID(t.Context(), pr.GetGitHeadRefName())