cmd/compile: add additional arm64 bit field rules

cmd/compile: add additional arm64 bit field rules

Get rid of TODO in prove pass.
We currently avoid marking shifts of constants as bounded, where
bounded means we don't have to worry about <0 or >=bitwidth shifts.
We do this because it causes different rule applications during lowering
which cause some codegen tests to fail.

Add some new rules which ensure that we get the right final instruction
sequence regardless of the ordering. Then we can remove this special case.

Change-Id: I4e962d4f09992b42ab47e123de5ded3b8b8fb205
Reviewed-on: https://go-review.googlesource.com/c/go/+/602935
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>