cmd/go: print deprecation messages for -i

build, install, and test will now print deprecation messages when the
-i flag is used. clean will continue to support -i.

For #41696

Change-Id: I956c235c487a872c5e6c1395388b4d6cd5ef817a
Reviewed-on: https://go-review.googlesource.com/c/go/+/266368


Trust: Jay Conrod <jayconrod@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>