debug/pe: recognize arm64 executables

debug/pe: recognize arm64 executables

We still need to add test data, but as yet we haven't identified
a good Windows arm64 compiler to produce small binaries.

This CL is part of a stack adding windows/arm64
support (#36439), intended to land in the Go 1.17 cycle.

Change-Id: Ifbecb9a6e25f7af38e20b7d7830df7f5efe2798a
Reviewed-on: https://go-review.googlesource.com/c/go/+/288820
Trust: Russ Cox <rsc@golang.org>
Trust: Jason A. Donenfeld <Jason@zx2c4.com>
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com>