HDDS-15375. Renames to prepare to switch SCM to the new versioning framework.

[errose28]

What changes were proposed in this pull request?

• Rename FUTURE_VERSION to UNKNOWN_VERSION in HDDSVersion and OzoneManagerVersion.

  • This provides a clearer fallback for when an unknown version is encountered on the disk within the server.

• Rename methods and variables using LayoutVersion terminology as needed since the term "layout version" will not be used going forward.

What is the link to the Apache JIRA

HDDS-15375

How was this patch tested?

No functional change. All existing tests should pass.

[sodonnel]

This change LGTM - are we ready to move it out of draft?

[errose28]

Some flaky upgrade related test showed up that I can't repro locally yet. I'd be surprised if it was caused by this but let me root cause it first.

[errose28]

Nevermind, not flaky I just had the wrong branch checked out. testNormalContainerUpgrade is failing because this PR changes the default version in DatanodeStorage from maxLayoutVersion (old HDDS layout version 10) to HDDSVersion.SOFTWARE_VERSION (new software version 100) without actually switching to the new version manager. Looks like this slipped in as part of the renames since I used AI to extract the rename-only changes from my development branch. I'll move that change to #10368 where it belongs. Relevant tests are passing on that PR's branch.