release-23.1: cloud,backupccl: path does not contain a completed latest backup (emp…

[blathers-crl]

Backport 1/1 commits from #106074 on behalf of @srosenberg.

/cc @cockroachdb/release

---

…ty objects ending with /)

Third-party services, e.g., AWS DataSync insert empty objects with a trailing / (to denote folders). Thus, a bucket containing backups which was transferred via AWS DataSync cannot be restored.
Previously, restore would fail with the follwing
error message, read LATEST path: path does not contain a completed latest backup: NoSuchKey.

This change skips over the empty object while enumerating the objects in the LatestHistoryDirectory.

Epic: none
Fixes: #106070

Release note (bug fix): cloud buckets containing backups can now be copied via AWS DataSync and other third-party services which insert empty object with a trailing /. Previously, restore would fail with the follwing error message, read LATEST path: path does not contain a completed latest backup: NoSuchKey.

---

Release justification: bug fix

[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?

[blathers-crl]

It looks like your PR touches production code but doesn't add or edit any test code. Did you consider adding tests to your PR?

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}

[cockroach-teamcity]

This change is 

[github-actions]

Reminder: it has been 3 weeks please merge or close your backport!