WireBytesStorage is the class used to access the wire bytes of a
function for compilation. It is stored and passed in a shared_ptr,
because it can be updated while compilation is running, and the
compilation threads will keep the old reference alive until the last
reference is dropped.
This CL fixes a few issues where we unnecessarily passed a reference
to the shared_ptr instead of just a raw pointer, and changes one
copy-assign into a move-assign to avoid an unneeded reference increase
and decrease.

R=thibaudm@chromium.org

Bug: v8:11879
Change-Id: I18b626a7b6cde09d5b29f091bd9f49d01d408206
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2953196Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75116}