support live migration with virtual persistent memory

Gerrit topic: https://review.opendev.org/#/q/topic:bp/support-live-migration-with-virtual-persistent-memory

Addressed by: https://review.opendev.org/695863
    support live migration with virtual persistent memory

Addressed by: https://review.opendev.org/687856
    support live migration with vpmems

Gerrit topic: https://review.opendev.org/#/q/topic:address-cleanup-issue

Addressed by: https://review.opendev.org/699148
    address specific resources cleanup issue

Gerrit topic: https://review.opendev.org/#/q/topic:bug/1841727

[efried 20200128] Spec merged, setting Definition:Approved.

Gerrit topic: https://review.opendev.org/#/q/topic:bp/name

Addressed by: https://review.opendev.org/708229
    Move 'live migration with vpmems' spec

Addressed by: https://review.opendev.org/708110
    bug-fix: Reject live migration with vpmem

[efried 20200220] Agreed in the Nova meeting to Direction:Approve all Definition:Approved blueprints http://eavesdrop.openstack.org/meetings/nova/2020/nova.2020-02-20-14.00.log.html#l-131

Gerrit topic: https://review.opendev.org/#/q/topic:working-branch

Gerrit topic: https://review.opendev.org/#/q/topic:support-live-migration-with-virtual-persistent-memory

Addressed by: https://review.opendev.org/678451
    Track orphan instances and error migrations in resource tracker

Addressed by: https://review.opendev.org/714064
    bug-fix: Reject live migration with vpmem

Addressed by: https://review.opendev.org/714593
    bug-fix: set do_cleanup always True for libvirt driver

Addressed by: https://review.opendev.org/714653
    Track orphan instances and error migrations in resource tracker

Addressed by: https://review.opendev.org/715362
    partial support for live migration with specific resources

[gibi 20200414] we hit feature freeze in Ussuri so I defer this to Victoria