PPC: Unify "runtime-style" IC functions with Runtime intrinsics

PPC: Unify "runtime-style" IC functions with Runtime intrinsics

Port bc8041dc2b4c8431c5c2476496acd3b7b8b3f61e

Original commit message:
    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.

R=danno@chromium.org, dstence@us.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1249433004

Cr-Commit-Position: refs/heads/master@{#29821}