cmd/compile: fix crawler for unexported fields with instantiated types
In markType() in crawler.go, mark the type of a unexported field if it
is a fully-instantiated type, since we create and instantiate the
methods of any fully-instantiated type that we see during import. As
before, we still do not mark the type of an unexported field if that
type is not generic. Fixes #48454 and most recent issue described in
48337. The included test is similar to the case in 48454.
Fixes #48454
Fixes #48337
Change-Id: I77a2a62b9e2647876facfa6f004201e8f699c905
Reviewed-on: https://go-review.googlesource.com/c/go/+/351315
Trust: Dan Scales <danscales@google.com> Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com> Reviewed-by: Keith Randall <khr@golang.org>