Draft: rpm-ostree: Rework backend to no longer use the DBus interface
Now that a few bugs are fixed in rpm-ostree, we can start relying on its caching logic instead of having our own internal one.
We also remove all DBus interface use as it is complex and error-prone, and we can all operations using the rpm-ostree command directly and parsing its JSON output.
This significantly simplifies the transaction logic.
Also add support for download size estimates for the Ostree Container Native path only (not available for the classic ostree format).
This should fix:
This is still pending some rpm-ostree fixes landing in a release:
This is based on !817 (merged) for convenience.
Still work in progress until I get all the rpm-ostree fixes in and do more testing.