1. Apply JSON conversion when -bench is in use.
2. Apply JSON conversion to "no test files" result.
3. Apply JSON conversion to test case-ending SKIP status.

Fixes #22769.
Fixes #22790.

Change-Id: I67ad656fc58bacae8c51d23b1e6d543cad190f08
Reviewed-on: https://go-review.googlesource.com/81535
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>