util/logs: request redactable logs by default

[jseldess]

PR: cockroachdb/cockroach#53263

From release notes:

The cockroach start and cockroach start-single-node commands now enable --redactable-logs by default. The flag is also enabled by default in cockroach demo if --log-dir is passed. This causes log files to become redactable, so that cockroach debug merge-log --redact or cockroach debug zip --redact can remove sensitive information from log files. (Reminder: cockroach debug zip --redact only affects log files; other items collected by the command can still contain sensitive information.) [#53263][#53263] {% comment %}doc{% endcomment %}

[jseldess]

Closed by #8708