Enable more revive linter rules (#30608)

Noteable additions:

- `redefines-builtin-id` forbid variable names that shadow go builtins
- `empty-lines` remove unnecessary empty lines that `gofumpt` does not
remove for some reason
- `superfluous-else` eliminate more superfluous `else` branches

Rules are also sorted alphabetically and I cleaned up various parts of
`.golangci.yml`.

(cherry picked from commit 74f0c84fa4245a20ce6fb87dac1faf2aeeded2a2)

Conflicts:
	.golangci.yml
	apply the linter recommendations to Forgejo code as well

models/repo/user_repo.go

@@ -135,7 +135,6 @@ func GetReviewers(ctx context.Context, repo *Repository, doerID, posterID int64)
 			// the owner of a private repo needs to be explicitly added.
 			cond = cond.Or(builder.Eq{"`user`.id": repo.Owner.ID})
 		}
-
 	} else {
 		// This is a "public" repository:
 		// Any user that has read access, is a watcher or organization member can be requested to review