The mutex is there to protect against concurrent compilation of the same
function. It can be avoided by accumulating the vector of call targets
locally in the LiftoffCompiler, and only transferring it to the stored
type feedback once at the end (under the mutex).

Also, choose slightly better data structures: base::OwnedVector uses
less memory that std::vector (because it never over-reserves), and
std::unordered_map is more memory efficient and faster to lookup that
{std::map}.

R=jkummerow@chromium.org

Bug: v8:13209
Change-Id: I7aa82560a83cbac5c019effc7fd38c9b1495a42c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3840294
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82602}