This moves the JSCreate related functionality from JSTypedLowering into
a dedicated JSCreateLowering reducer. This is in preparation of landing
the support for optimized literals in TurboFan, which would blow up
JSTypedLowering quite seriously otherwise.

R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/1678833002

Cr-Commit-Position: refs/heads/master@{#33813}