log: properly handle malformed log files in json log formatting

A [recent PR](https://github.com/cockroachdb/cockroach/pull/163224) was merged to fix a bug that caused nodes too OOM and crash. The fix that this PR implemented is a bandaid fix that was safe to backport, but a real fix should be implemented so that json log decoding properly handles the case where malformed logs are written to log files configured with the JSON logging format.

See https://github.com/cockroachdb/cockroach/issues/163364 for more information about the original issue the linked PR fixed

Jira issue: CRDB-61275

Start by reviewing the linked PR #163224 and issue #163364, then trace the JSON log decoding path for log files configured with JSON formatting. Done means malformed log entries are handled without causing node OOM or crashes while JSON log processing remains functional.

Written by the indexing model from the issue text.