chore: still keep ctx in git.Repository struct for cat-file batch command (#38684)

Unfortunately, we can't completely remove the ctx from git.Repository,
because the CatFileBatch still heavily depends on a parent context.

If we remove the Repository ctx, the CatFileBatch will become a mess and
create a lot of unnecessary git processes.

http://localhost:3000/-/admin/monitor/perftrace

* Before: open a repo home, dozens of git processes (duplicate cat-file)
* After: only a few (no duplicate cat-file)

routers/api/v1/repo/pull.go

@@ -1106,7 +1106,7 @@ func parseCompareInfo(ctx *context.APIContext, compareParam string) (result *git
 		headGitRepo = ctx.Repo.GitRepo
 		closer = func() {} // no need to close the head repo because it shares the base repo
 	} else {
-		headGitRepo, err = git.OpenRepository(headRepo)
+		headGitRepo, err = git.OpenRepository(ctx, headRepo)
 		if err != nil {
 			ctx.APIErrorInternal(err)
 			return nil, nil

routers/api/v1/repo/wiki.go

@@ -467,7 +467,7 @@ func findEntryForFile(ctx *context.APIContext, wikiRepo *git.Repository, commit
 // findWikiRepoCommit opens the wiki repo and returns the latest commit, writing to context on error.
 // The caller is responsible for closing the returned repo again
 func findWikiRepoCommit(ctx *context.APIContext) (*git.Repository, *git.Commit) {
-	wikiRepo, err := git.OpenRepository(ctx.Repo.Repository.WikiStorageRepo())
+	wikiRepo, err := git.OpenRepository(ctx, ctx.Repo.Repository.WikiStorageRepo())
 	if err != nil {
 		ctx.APIErrorAuto(err)
 		return nil, nil