runtime: deduplicate context call injection on Windows
Injecting a call to a thread context is complex enough to warrant
a dedicated function so that we don't repeat the same code in multiple
places. Note that the unix sigctxt struct also follows the
same approach.
The behavior is unchanged, but the implementation semantics are now
clearer by using goarch.StackAlign instead of a mix of goarch.PtrSize,
goarch.StackAlign and hardcoded values.
While here, fix #68552.
Cq-Include-Trybots: luci.golang.try:gotip-windows-arm64
Change-Id: Ic29cd2bf322b520127fecccafd61577076945758
Reviewed-on: https://go-review.googlesource.com/c/go/+/657815 Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: David Chase <drchase@google.com>