This adds the implementation of the {AssemblerBufferCache} class.
PKU-protected memory is allocated via the {WasmCodeManager}, which has
access to the actual protection key.

R=thibaudm@chromium.org

Bug: v8:12809
Change-Id: Id26abd6f98248d5c646ae337ccb903d3e168bed1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3593137Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80181}