Update default ubuntu images for pipelines

[c-ryan-k]

We've started getting warnings as ubuntu-18.04 images are deprecated on ADO.

This update pushes our ubuntu images up to 20.04 (which is also the same as ubuntu-latest currently), but also provides support for testing pipelines on ubuntu 22.04

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[vilit1]

pipeline run?

[c-ryan-k]

pipeline run?

Merge was completed in this PR, waiting for some other pipelines to finish before I kick off dry-runs of the nightly and release pipelines to ensure we're good on 20.04 at least.

May do some testing today or tomorrow to try out 22.04, but think this is safe to include as a runtime option since it isn't a default value.

[digimaun]

Lets get this in soon

[c-ryan-k]

Lets get this in soon

Trying to pin down a test failure in ADT while running this merge branch against our current release pipeline. Not sure if it's at all related to the jump from 18 to 20, but want to verify and see the ADT tests pass on 20 before moving forward.

If necessary, I can also modify this PR to still set the default to 20.04, but leave 18.04 as an option for break-glass scenarios if we need a release and 20 is failing for some reason.