Use inline asm to generate the x64 PushAllRegistersAndIterateStack
which is the trampoline for conservative stack scanning. Keep the
function definition as C code to allow clang to generate the correct
mangling for each platform.

This approach has the benefit that it immediately works for all
platforms that support clang.

Bug: chromium:1056170
Change-Id: Ic7a1c1b57e67ae1442bd8bda4e55d89112facfc7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2132787Reviewed-by: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66958}