Handle mmap failures and memory occupied by other programs #1351
Description
When MMTk uses a predefined heap range, and fails to mmap the required memory, MMTk should be able to step through these 'holes' in its heap, and continue to work.
This only applies to the heap memory, and does not apply to the side metadata memory. We have strict mapping between data range to side metadata range. MMTk should quarantine side metadata memory to avoid such situations.