The CompilationPhase helper class is only used in Crankshaft and is not
suitable for use in other compilers. This factors is out into a separate
file and moves it into the "crankshaft" directory.

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/1758773002

Cr-Commit-Position: refs/heads/master@{#34441}