This patch adds fast paths for @@replace and @@split that call into
the old, side-effect free (and faster) versions of those builtin
operations when possible (roughly, when the receiver is a RegExp
and the 'exec' method is untampered). Also add some micro-optimizations
that further improve performance.

Taken altogether, this takes us from a ~70% regression on the Octane
RegExp benchmark to a ~9% regression.

The test262.status lines for RegExps has been reorganized to make it
clearer the status of individual tests. More work will likely be
required to increase spec compliance before the --harmony-regexp-exec
flag is shipped; some of that work is happening on the spec side.

BUG=v8:4602
LOG=y

Review URL: https://codereview.chromium.org/1836123002

Cr-Commit-Position: refs/heads/master@{#35118}