Release v4.3.0

This release moves the new swupd and chroot functionality out from
behind --new-swupd and --new-chroots, making it the standard behavior
for all users. The flags are left as deprecated to not break scripts,
but they should be removed by users going forward.

Additional improvements in this release include clearing out DNF state
files from the internal chroot representation, and removing an error
response from the delta pack generation in the case that --to == --from.