feat(cli) Clearly output what version upgrade is being considered

[isms]

Many users seem to be confused about why they are getting errors saying Failed to connect to an apt repository. You may not be connected to the Internet.:

• Failed to connect to an apt repository beta#15
• pop-upgrade: dbus client error: calling ReleaseUpgradeFinalize method failed (upgrade from 18.04) beta#36
• 20.04 upgrade "You may not be connected to the Internet." error beta#45
• Pop!_OS Upgrade to 20.04 fails #97

At least some of these users are probably trying to check that their upgrade to 20.04 was complete. When they are doing so, the tool actually tries to upgrade to (and fails to reach repos for) 20.10.

Behavior / steps to reproduce

This is what you see when you run sudo pop-upgrade release upgrade systemd -f on the most recent release:

Event: removing deprecated and/or conflicting packages
Event: updating package lists for the current release
Event: fetching updated packages for the current release
Event: upgrading packages for the current release
Event: ensuring that system-critical packages are installed
Event: updating the source lists to the new release
Failed to connect to an apt repository. You may not be connected to the Internet.

Expected

1. A message at the beginning saying something like Found 20.04, attempting to upgrade to 20.10
2. An error message or logging on NoConnection that shows which repository requests failed. For some of the users who were confused above, seeing that it was trying to reach 20.10 repos would have answered the question.