This refactors the OptimizedCompileJob class to be agnostic from the
actual underlying compiler. Instead it represents a base class for all
compilation jobs. The implementation is provided by the backend by just
overriding the phase methods.

Also note that this contains the semantics change of not falling back to
Crankshaft when TurboFan optimization fails. This fallback is no longer
needed and will not be supported going forward.

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/1872483002

Cr-Commit-Position: refs/heads/master@{#35377}