Rollup merge of #133875 - onur-ozkan:early-return-rustfmt, r=jieyouxu

handle `--json-output` properly

Because `rustfmt` doesn't support JSON output, `x test --json-output` doesn't respect the `--json-output` flag during formatting step. This change makes that `x test` skips the formatting step if `--json-output` is specified. In addition, resolves #133855 with the 2nd commit.

Author: matthiaskrgr