The previous code cache system required stubs to be marked with a StubType, causing them to be inserted either into a fixed array or into a dictionary-mode code cache. This could cause names to be in both cases, and lookup would just find the "fast" one first. Given that we clear out the caches on each GC, the memory overhead shouldn't be too bad. Additionally, the dictionary itself should just stay linear for small arrays; that's faster anyway.

This CL additionally deletes some dead IC code.

BUG=

Review URL: https://codereview.chromium.org/1846963002

Cr-Commit-Position: refs/heads/master@{#35291}