cmd/compile: fix generic type handling in crawler

There are a bunch of nodes beside ONAME and OTYPE, (such as OSTRUCTLIT
and OCOMPLIT) which can introduce a generic type that we need to mark.
So, just mark any generic type on any node in markInlBody. In this
particular issue, the type is introduced by an OSTRUCTLIT node.

Updates #48337

Change-Id: I271932518f0c1fb54d91a603e01a855c69df631d
Reviewed-on: https://go-review.googlesource.com/c/go/+/349909


Trust: Dan Scales <danscales@google.com>
Trust: Carlos Amedee <carlos@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>