cmd/go/internal: update documentation of go test and go generate
Fixes #57050
Change-Id: I46cac667ff78ac171c878f4366f8f01f58f1d27d
GitHub-Last-Rev:
697c255ece18cd4772b76d62991474a7da2536d8
GitHub-Pull-Request: golang/go#57814
Reviewed-on: https://go-review.googlesource.com/c/go/+/461683
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>