cmd/compile: test register ABI for method, interface, closure calls

cmd/compile: test register ABI for method, interface, closure calls

This is enabled with a ridiculous magic name for method,
or for last input type passed, that needs to be changed
to something inutterable before actual release.

Ridiculous method name: MagicMethodNameForTestingRegisterABI
Ridiculous last (input) type name: MagicLastTypeNameForTestingRegisterABI

RLTN is tested with strings.Contains, so you can have
MagicLastTypeNameForTestingRegisterABI1
and
MagicLastTypeNameForTestingRegisterABI2
if that is helpful

Includes test test/abi/fibish2.go

Updates #44816.

Change-Id: I592a6edc71ca9bebdd1d00e24edee1ceebb3e43f
Reviewed-on: https://go-review.googlesource.com/c/go/+/299410
Trust: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>