manager: add taint flag "support-ended"

manager: add taint flag "support-ended"

In the welcome line, use NAME= as the fallback for PRETTY_NAME=.
PRETTY_NAME= doesn't have to be set, but NAME= should.

Example output:
---
Welcome to Fedora Linux 37 (Rawhide Prerelease)!

[  !!  ] This OS version (Fedora Linux 37 (Rawhide Prerelease)) is past its end-of-support date (1999-01-01)
Queued start job for default target graphical.target.
[  OK  ] Created slice system-getty.slice.
---