Some context: actions/runner-images#11101

Note that there are 8-hour scheduled Ubuntu 20.04 outage periods on March 4, 11, 18, and 25 where jobs attempting to use Ubuntu 20.04 will fail. I do not know if such jobs will fail with some random probability, or 100% of the time, during those periods.

• Replace most mentions of Ubuntu 20.04 with 22.04 #5156 updates most of the p4c CI tests that currently use Ubuntu 20.04, to use Ubuntu 22.04 instead. It does not update all of them, because the two CI tests listed below are failing when I tried updating them, so it would be nice to track them separately.
• ptf-ebpf fails if you simply try to update Ubuntu 20.04 to 22.04 with no other changes. See Update ptf-ebpf CI test to Ubuntu 22.04 #5159 for an attempted PR that does this, and some details of its failure in its logs.
• validate-p4c fails if you simply try to update Ubuntu 20.04 to 22.04 with no other changes. See Update validate-p4c CI test to use Ubuntu 22.04 #5160 for an attempted PR that does this, and some details of its failure in its logs.

If someone really, really wants to continue CI tests using Ubuntu 20.04, I recommend that they figure out how to do so and implement it. I am not motivated to do so, as I am personally OK if we stop CI tests on Ubuntu 20.04.

I think a higher priority should be given to starting CI tests on Ubuntu 24.04.