internal/runtime/syscall/windows: factor out code from runtime

internal/runtime/syscall/windows: factor out code from runtime

Factor out the code related to doing calls using the Windows stdcall
calling convention into a separate package. This will allow us to
reuse it in other low-level packages that can't depend on syscall.

Updates #51087.

Cq-Include-Trybots: luci.golang.try:gotip-windows-arm64,gotip-windows-amd64-longtest,gotip-solaris-amd64
Change-Id: I68640b07091183b50da6bef17406c10a397896e9
Reviewed-on: https://go-review.googlesource.com/c/go/+/689156
Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>