This adds the next step to freeing code: We free the actual C++
{WasmCode} objects. This will cause UAF if any C++ code uses stale
references.
The underlying machine code will still not be freed.

For simplicity, this CL changes the vector of owned_code to an ordered
set, such that lookup and removal is much simpler. The drawback is that
insertion is now more expensive.

R=mstarzinger@chromium.org

Bug: v8:8217
Change-Id: I07fc81167816637fbaad6c06ff79e3f952f2fde8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1593080
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61165}