Merge changes I76ce981e,Ifd00d52e,Ibc6fa38b,Ic3aa6a74

* changes:
  scudo: Support memory tagging in the secondary allocator.
  [scudo/standalone] Use .arch_extension memtag, not mte
  [GWP-ASan] Add aligned allocations.
  [scudo/standalone] Use zx_system_get_page_size() on Fuchsia