We kept the CodeMap filled with entries between profiles, even in
kLazyLogging mode which will re-fill the CodeMap when profiling starts
again. See the bug for more details.

This fix manually clears the CodeMap after the last profile is deleted.
We already call DisableLogging() when the last profile is stopped. At
this point we still need the CodeMap alive because the profile object
we expose via the API is backed by the CodeEntry objects in the CodeMap.
Once the last profile is deleted though, we can empty the CodeMap.

There is still another bug, which is that we never delete CodeEntry
objects for deleted code, as there are no CodeDeleteEvents from the GC.
We will work on that separately, but this fix should stop those leaks
accumulating between profiles as we wipe the CodeMap entirely between
profiles (at least for kLazyLogging mode). kEagerLogging mode still has
this problem and will only be fixed by introducing CodeDelete events or
similar.

Bug: v8:11051
Change-Id: Iab9570747d17c657e6e318d434f935af8047d05f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2491033
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Reviewed-by: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70792}