DAOS-16818 common: Evict NE memory bucket when empty - MD_ON_SSD_p2

[sherintg]

Pre-enabler changes to umem_cache_map routine to enable allocator to mark a non-evictable page as evictable and visa-versa. The allocator will make use of the above changes as follows:

• When all memory blocks in a non-evictable page is marked unused, allocator can mark the entire page as unused and will notify the umem_cache to mark the page as evictable. No further allocations from this memory block will happen from now ownwards.
• Allocator will request the umem_cache to map the page again as non-evictable when there is a need to extend non-evictable region or as evictable page when a new evictable page has to be reserved.

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• Two review approvals and any prior change requests have been resolved.
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[github-actions]

Ticket title is 'Evict NE memory bucket when empty - MD_ON_SSD_p2'
Status is 'Open'
Labels: 'hpe,md_on_ssd2'
https://daosio.atlassian.net/browse/DAOS-16818