release-23.2: spec: move machine type, zone, local ssd defaults out of the TestSpec and the registry

[RaduBerinde]

Backport 4/4 commits from #111811.

/cc @cockroachdb/release

Release justification: test-only change, keeping roachtest in updated on release branches.

---

This set of commits makes more progress towards #104029 and - more generally - not baking in any flag configuration into the registry itself.

spec: move RoachprodOpts args to separate struct

Epic: none
Release note: None

spec: move default machine type from ClusterSpec to RoachprodClusterConfig

This is much more logical and allows the removal of the parameter from
the registry.

Epic: none
Release note: None

spec: move default zones to RoachprodClusterConfig

Remove the default zones from ClusterSpec (and the registry), and
add it to RoachprodClusterConfig.

Epic: none
Release note: None

spec: move local SSD preference to RoachprodClusterConfig

We change the boolean in the TestSpec to a tri-state (default, prefer
on, disable). This way we can apply the default when creating the
cluster.

Epic: none
Release note: None

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Backports should only be created for serious
  issues or test-only changes.
• Backports should not break backwards-compatibility.
• Backports should change as little code as possible.
• Backports should not change on-disk formats or node communication protocols.
• Backports should not add new functionality (except as defined
  here).
• Backports must not add, edit, or otherwise modify cluster versions; or add version gates.
• All backports must be reviewed by the owning areas TL and one additional
  TL. For more information as to how that review should be conducted, please consult the backport
  policy.

If your backport adds new functionality, please ensure that the following additional criteria are satisfied:

• 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. State changes must be further protected such that nodes running old binaries will not be negatively impacted by the new state (with a mixed version test added).
• The PM and TL on the team that owns the changed code have signed off that the change obeys the above rules.
• Your backport must be accompanied by a post to the appropriate Slack
  channel (#db-backports-point-releases or #db-backports-XX-X-release) for awareness and discussion.

Also, please add a brief release justification to the body of your PR to justify this
backport.

[cockroach-teamcity]

This change is 

[RaduBerinde]

I somehow thought this change made it into the release-23.2 branch when it was cut, but I was wrong.

[RaduBerinde]

https://teamcity.cockroachdb.com/viewLog.html?buildId=12603648

[RaduBerinde]

TFTR!