With eager compilation, CompilationEventCallbacks get released when all
compilation units in the compilation state are finished. This is
possible because no future compilation event could get triggered after
that. With dynamic tiering, though, the {FinishedCompilationChunk} event
can trigger repeatedly, even after all compilation units finish at some
point in time, as dynamic tiering can create new CompilationUnits. As
a temporary fix, CompilationEventCallbacks don't get released when
dynamic tiering is enabled.

This CL fixes this issue by turning the callback from an std::function
into a class, and adding a second function to the class which indicates
whether the callback can be released when all compilation units in the
compilation state are finished. Thereby all callbacks can be deallocated
except the ones like the code caching callback which waits for the
{FinishedCompilationChunk} events.

R=jkummerow@chromium.org

Bug: v8:12289
Change-Id: I0f73f4bd2dffe644c9a26c274cb52ac6fa49ab67
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3264288
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77890}