- Move LsanPageAllocator to base;
- Use LsanPageAllocator in PageBackend that serves managed C++
  objects;
- Remove spurious TODO for GCInfoTable which should not use the
  LSAN-aware backend;

Bug: chromium:1056170
Change-Id: I2caa11443ab44da5164f1c29339e302bffb49228
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2850157
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74192}