Add stat to ToCommit function for speed (#21337)

Calls to ToCommit are very slow due to fetching diffs, analyzing files.
This patch lets us supply `stat` as false to speed fetching a commit
when we don't need the diff.

/v1/repo/commits has a default `stat` set as true now. Set to false to
experience fetching thousands of commits per second instead of 2-5 per
second.

routers/api/v1/repo/pull.go

@@ -1306,7 +1306,7 @@ func GetPullRequestCommits(ctx *context.APIContext) {
 
 	apiCommits := make([]*api.Commit, 0, end-start)
 	for i := start; i < end; i++ {
-		apiCommit, err := convert.ToCommit(ctx.Repo.Repository, baseGitRepo, commits[i], userCache)
+		apiCommit, err := convert.ToCommit(ctx.Repo.Repository, baseGitRepo, commits[i], userCache, true)
 		if err != nil {
 			ctx.ServerError("toCommit", err)
 			return