... on Code objects.

Refactors: create a dedicated WasmCode constructor, hide the internal
constructor, constify members, and let SafepointTable handle
out-of-line tables.

Expose a new Code::SafepointTableAddress() helper as the source of
truth. Some safepoint tables may move out-of-line in the near future.

Bug: v8:7777,v8:10707
Change-Id: I4e2d954ed2d157235e9dfa3e7a5ca08800896683
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2297459Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68837}