Now that embedded builtins are mandatory and non-embedded builtins no
longer need to be supported, it is safe to embed the target of the
CEntry builtin directly into WebAssembly runtime stubs. This produces
more efficient code and simplifies the runtime stubs.

R=clemensb@chromium.org

Change-Id: If2f91fa733edc266af3a204ac17ff36e4c0b41a3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1895567
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64739}