The patch makes it manage a free list of released code_entries_ slots,
and reuse the slots as needed.

BUG=v8:7719

Change-Id: I07df1ce983fe00e0ca3d1a1ea20e1a141aabad99
Reviewed-on: https://chromium-review.googlesource.com/1062769Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Commit-Queue: Alexei Filippov <alph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53314}