This is preparatory cleanup work for eventually tracking the functions
(rather than concrete closures) in the CALL_IC, also for builtins like
the default PromiseCapability [[Resolve]] and [[Reject]] functions. It
adds a new FeedbackCell type, which is used by JSFunctions consistently
now to reference the feedback vector (or undefined if not the function
is not compiled yet or is a native/asm.js function).

This also changes the calling convention for FastNewClosure builtin and
the JSCreateClosure operator in TurboFan to carry the FeedbackCell here
instead of the parent FeedbackVector and the slot index. In addition we
eliminate the now unused %InterpreterNewClosure runtime function.

Bug: v8:2206, v8:7253, v8:7310
Change-Id: Ib4ce456e276e0273e57c163dcdd0b33abf863656
Reviewed-on: https://chromium-review.googlesource.com/928403
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51474}