Modify the cctests for the inlined JS-to-Wasm calls to use the
%ObserveNode intrinsic, to verify that the JSCall node is actually
inlined . This requires a small refactoring of the %ObserveNode
implementation.

Bug: v8:11092
Change-Id: I01727143fec64c6c11c58b1b664f51daae5bfdb6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2677811
Commit-Queue: Paolo Severini <paolosev@microsoft.com>
Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72838}