ostree/dump: Include collection IDs and mirrored refs in summary dumps

ostree/dump: Include collection IDs and mirrored refs in summary dumps

If a repository’s summary file includes a collection ID, output that. If
it includes refs from other collections (in the ‘collection map’), output
those and include the same metadata detail as for refs in the summary
file’s main refs map.

If collection IDs are specified in the summary file, this changes the
output format from `ostree summary -v` to use (collection ID, ref name)
tuples.

Signed-off-by: Philip Withnall <withnall@endlessm.com>
Closes: #924
Approved by: cgwalters