release-22.2: roachprod: add COCKROACH_UPGRADE_TO_DEV_VERSION to DefaultEnvVars

[blathers-crl]

Backport 1/1 commits from #88005 on behalf of @srosenberg.

/cc @cockroachdb/release

---

Recent changes to cockroach_versions (logic) now require setting COCKROACH_UPGRADE_TO_DEV_VERSION environment variable in order to allow upgrading a stable release data-dir to a dev. version. The PR [1] which introduced this env. var. did not correctly backport the change to all the roachtests which perform this type of upgrade.

Since all roachtests which exercise upgrade paths are intended to test this upgrade scenario, we set COCKROACH_UPGRADE_TO_DEV_VERSION by default in roachprod instead of polluting the roachtests with more config. settings.

Consequently, MakeClusterSettings now returns the default ClusterSettings which includes COCKROACH_UPGRADE_TO_DEV_VERSION; generateStartCmd ensures it's passed into cockroach env. via start.sh.

Release note: None

Release justification: bug fix in roachtests.

Resolves:
#87675
#87687

[1] #87468

---

Release justification:

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Patches should only be created for serious issues or test-only changes.
• Patches should not break backwards-compatibility.
• Patches should change as little code as possible.
• Patches should not change on-disk formats or node communication protocols.
• Patches should not add new functionality.
• Patches must not add, edit, or otherwise modify cluster versions; or add version gates.

If some of the basic criteria cannot be satisfied, ensure that the exceptional criteria are satisfied within.

• There is a high priority need for the functionality that cannot wait until the next release and is difficult to address in another way.
• The new functionality is additive-only and only runs for clusters which have specifically “opted in” to it (e.g. by a cluster setting).
• New code is protected by a conditional check that is trivial to verify and ensures that it only runs for opt-in clusters.
• The PM and TL on the team that owns the changed code have signed off that the change obeys the above rules.

Add a brief release justification to the body of your PR to justify this backport.

Some other things to consider:

• What did we do to ensure that a user that doesn’t know & care about this backport, has no idea that it happened?
• Will this work in a cluster of mixed patch versions? Did we test that?
• If a user upgrades a patch version, uses this feature, and then downgrades, what happens?

[cockroach-teamcity]

This change is 

[dt]

In theory we don't need this on the release branch since it doesn't identify itself as a dev build

[srosenberg]

In theory we don't need this on the release branch since it doesn't identify itself as a dev build

Good point, closing!