Previous to this CL, ICs used a slightly different code idiom
to get to C++ code from generated code than runtime intrinsics,
using an IC_Utility class that in essence provided exactly
the same functionality as Runtime::FunctionForId, but in its
own quirky way.

This CL unifies the two mechanisms, folding IC_Utility
away by making all IC entry points in C++ code, e.g. IC
miss handlers, full-fledged runtime intrinsics. This makes
it possible to eliminate a bunch of ad-hoc declarations and
adapters that the IC system had to needlessly re-invent.

As a bonus and the original reason for this yak-shave:
IC-related C++ runtime functions are now callable from
TurboFan.

Review URL: https://codereview.chromium.org/1248303002

Cr-Commit-Position: refs/heads/master@{#29811}