This enables using TNode types without including code-assembler.h,
which is useful when generating CallInterfaceDescriptors.

As a drive-by, this moves TNode from v8::internal::compiler to
v8::internal. It's only used outside of the compiler anyway.

Change-Id: I3d938c22366a3570315041683094f77b0d1096a2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1798425
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63721}