debug: create CLI command that *only* downloads logs

**Is your feature request related to a problem? Please describe.**
Right now, the only way to get a dump of logs from a cluster is through running the `debug zip`. The bundle produced by this command can sometimes contain gigabytes worth of data, which is cumbersome to handle.

Observability teams are working on finding ways to get other important structured information out of debug zip to be viewable elsewhere, but the need to view dumps of unredacted logs in compliant environments will likely not go away any time soon. We need a way to fetch this information in a more lightweight fashion without pulling the entire kitchen sink, like we do with a debug zip.

**Describe the solution you'd like**
Create a new debug command that only fetches a zip file containing logs.

**Describe alternatives you've considered**
We could also achieve this by providing some type of filter to the existing debug zip command to only fetch logs.

Jira issue: CRDB-27466

Start by inspecting the existing `debug zip` CLI command and the log-collection path it uses. The work is done when a debug command can produce a zip containing only logs, without downloading the other debug data included by `debug zip`.

Written by the indexing model from the issue text.