release-23.2: clusterversion: bump min supported version to 23.1

[RaduBerinde]

Backport 1/1 commits from #112122.

/cc @cockroachdb/release

Release justification: this change effectively disables version skipping when upgrading to 23.2.

---

This commit changes the minimum supported version to 23.1. It is
intended to be backported to release-23.2.

Tests that had to be modified mostly fall in one of two categories:

• tests that verify a release-specific behavior involving 22.2 or
  in-development versions of 23.1; these tests were deleted.
• tests that verify general version handling logic but used specific
  versions; I tried to make these use the min supported version or a
  new VCurrent_Start constant.

The logic tests required a bunch of work because we were missing a
local-mixed-23.1 config, which should have been added early in the
23.2 cycle. Without this config, all test directives related to 23.2
features were conditioned on local-mixed-22.2-23.1 (i.e. lumped in
with 23.1 features). I added the new config and let the test failures
guide me; most of the cases that needed to be conditioned on
local-mixed-23.1 where around the bigger 23.2 features (isolation
levels, procedures). In subsequent release cycles, we will create the
new config as soon as possible.

This commit does not remove the obsolete in-development 23.1 version
keys and related code; that will be done separately.

Informs: #111760
Epic: REL-506
Release note: None

[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