[dev.typeparams] cmd/compile: rewrite method calls during typecheck

CL 330671 move rewriting method call to method expression to escape
analysis. This CL move the rewriting up further, into typecheck. It
helps simplify the code for dowstream passes, as they now only have to
deal with OCALLFUNC.

There're two notes:

 - For -G=3, we can't rewrite d.M() where d is an instantiated receiver
   in transformCall, but let irgen.stencil to rewrite it.

 - Escape analysis still have to check for rewriting method calls, as
   the devirtualization pass can still generate OCALLMETH.

Does not pass toolstash, since when the export data now contains method
expression calls instead of method calls.

Change-Id: I77465ef04d50dc4efedddca7eb55b3fc9483db0e
Reviewed-on: https://go-review.googlesource.com/c/go/+/330831


Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>