cmd/go: add hints to more missing sum error messages

When a command fails due to a module zip sum missing from go.sum,
if the module is in the build list, the go command will print a
'go mod download' command the user can run to fix it.

Previously, a hint was only printed if the module provided a package
in 'all'. We don't print a 'go get' hint, since we may not want to add
a new requirement to go.mod.

Fixes #43572

Change-Id: I88c61b1b42ad56c04e4482f6a1bb97ce758aaeff
Reviewed-on: https://go-review.googlesource.com/c/go/+/282712


Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Trust: Jay Conrod <jayconrod@google.com>