Refactors find_executable_vm_areas() to share its map entry skipping with the re-takeover re-walk from b06a7022, but not its module list or executable area updates. This entry skipping for vmheap turns out to make a big performance difference when attaching.
Removes individual updates to memcache for entries inside vmheap which were already bulk-added for the find_executable_vm_areas() walk.
Issue: #2037 (closed)