librbd: update progress for non-existent objects on deep-copy

librbd: update progress for non-existent objects on deep-copy

As a side effect of commit e5a21e904142 ("librbd: deep-copy image copy
state machine skips clean objects"), handle_object_copy() stopped being
called for non-existent objects.  This broke progress_object_no logic,
which expects to "see" all object numbers so that update_progress()
callback invocations can be ordered.  Currently update_progress() based
progress reporting gets stuck after encountering a hole in the image.

To fix, arrange for handle_object_copy() to be called for all object
numbers, even if ObjectCopyRequest isn't created.  Defer the extra call
to the image work queue to avoid locking issues.

Fixes: https://tracker.ceph.com/issues/56181
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
(cherry picked from commit 6813a7879146aec40f204a174b40a5a54e00b780)

Conflicts:
	src/librbd/deep_copy/ImageCopyRequest.cc [ commit aabfb76e51bf
	  ("librbd: swapped ThreadPool/ContextWQ for AsioEngine") not in
	  octopus ]
	src/test/librbd/deep_copy/test_mock_ImageCopyRequest.cc [
	  commit 235b27a8f08a ("librbd/deep_copy: skip snap list if
	  object is known to be clean") not in octopus ]