Stubs and builtins are very similar. The main differences are that
stubs can be parameterized and may be generated at runtime, whereas
builtins are generated at mksnapshot-time and shipped with the snapshot
(or embedded into the binary).

My main motivation for these conversions is that we can generate
faster calls and jumps to (embedded) builtins callees from (embedded)
builtin callers. Instead of going through the builtins constants table
indirection, we can simply do a pc-relative call/jump.

This also unlocks other refactorings, e.g. removal of
CallRuntimeDelayed.

TBR=mlippautz@chromium.org

Bug: v8:6666
Change-Id: I4cd63477f19a330ec70bbf20e2af8a42fb05fabb
Reviewed-on: https://chromium-review.googlesource.com/1044245Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53027}