Insertion into the map is expensive, hence avoid inserting every single
code object. Instead, collect them in a {std::vector}, and only insert
them when the {owned_code_} map is being used. By sorting the vector
before inserting into the map, we can make most insertions constant time
instead of logarithmic in the size of the map, by using the previous
insert position as a hint for the next one.

Drive-by: Remove an unneeded {WasmCodeRefScope}.

R=thibaudm@chromium.org

Bug: v8:11164
Change-Id: I3cc47f627eca40ea747d3e8388f93094650bbe19
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2656259Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72423}