This is another step towards making calls to builtins more convenient.

Builtins::CallableFor is an automatically generated Callable accessor for TFS
builtins (whereas previously we had to manually add an accessor to
code-factory.{h,cc}).

CSA::CallBuiltin is a convenience wrapper around CallStub for TFS builtins.

We can begin removing accessors for TFS builtins from CodeFactory in an
upcoming commit.

BUG=v8:5737

Review-Url: https://codereview.chromium.org/2752213002
Cr-Commit-Position: refs/heads/master@{#43865}