server, log: Malformed log entries make /_status/logs return 500

[alyshanjahani-crl]

Describe the problem

When a node has logs that contain a panic, the logs API on the status server fails as the panic causes log.FetchEntriesFromFiles to return an ErrMalformedLogEntry.

To Reproduce

This occurs quite often during the db-console/mixed-version-endpoints roachtest. See #149866 (comment)

Expected behavior
A panic in a log file shouldn't cause the status server to fail to serve the logs.

Jira issue: CRDB-53311

[blathers-crl]

Hi @alyshanjahani-crl, please add branch-* labels to identify which branch(es) this C-bug affects.

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