For various reasons we need an internal-facing imports API. Move imports
to internal/imports, leaving behind a small wrapper package. The wrapper
package captures the globals at time of call into the options struct.
Also converts the last goimports tests to use the test helpers, and
fixes go/packages in module mode to work with empty modules, which was
necessary to get those last tests converted.
Change-Id: Ib1212c67908741a1800b992ef1935d563c6ade32
Reviewed-on: https://go-review.googlesource.com/c/tools/+/175437
Run-TryBot: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Cottrell <iancottrell@google.com>
