Merge db.Iterate and IterateObjects (#21641)

These two functions are similiar, merge them.

modules/doctor/breaking.go

@@ -18,10 +18,9 @@ import (
 func iterateUserAccounts(ctx context.Context, each func(*user.User) error) error {
 	err := db.Iterate(
 		ctx,
-		new(user.User),
 		builder.Gt{"id": 0},
-		func(idx int, bean interface{}) error {
-			return each(bean.(*user.User))
+		func(ctx context.Context, bean *user.User) error {
+			return each(bean)
 		},
 	)
 	return err

modules/doctor/fix16961.go

@@ -269,13 +269,10 @@ func fixBrokenRepoUnits16961(ctx context.Context, logger log.Logger, autofix boo
 
 	err := db.Iterate(
 		ctx,
-		new(RepoUnit),
 		builder.Gt{
 			"id": 0,
 		},
-		func(idx int, bean interface{}) error {
-			unit := bean.(*RepoUnit)
-
+		func(ctx context.Context, unit *RepoUnit) error {
 			bs := unit.Config
 			repoUnit := &repo_model.RepoUnit{
 				ID:          unit.ID,

modules/doctor/mergebase.go

@@ -21,10 +21,9 @@ import (
 func iteratePRs(ctx context.Context, repo *repo_model.Repository, each func(*repo_model.Repository, *issues_model.PullRequest) error) error {
 	return db.Iterate(
 		ctx,
-		new(issues_model.PullRequest),
 		builder.Eq{"base_repo_id": repo.ID},
-		func(idx int, bean interface{}) error {
-			return each(repo, bean.(*issues_model.PullRequest))
+		func(ctx context.Context, bean *issues_model.PullRequest) error {
+			return each(repo, bean)
 		},
 	)
 }

modules/doctor/misc.go

@@ -30,10 +30,9 @@ import (
 func iterateRepositories(ctx context.Context, each func(*repo_model.Repository) error) error {
 	err := db.Iterate(
 		ctx,
-		new(repo_model.Repository),
 		builder.Gt{"id": 0},
-		func(idx int, bean interface{}) error {
-			return each(bean.(*repo_model.Repository))
+		func(ctx context.Context, bean *repo_model.Repository) error {
+			return each(bean)
 		},
 	)
 	return err