util/log: automatic log redaction

[jseldess]

PR: cockroachdb/cockroach#48051

From release notes:

The commands cockroach debug zip and cockroach debug merge-logs support a new flag --redact-logs. When specified, it causes log messages that potentially contain confidential data or PII to be redacted away. This feature is experimental. Note: Currently, this redaction is extremely aggressive and may hinder the ability of Cockroach Labs to investigate issues from log files, especially if --redactable-logs is not enabled server-side. Other potentially-confidential data may still be retrieved by cockroach debug zip; the new flag only applies to retrieved log files inside the output zip file. [#48051][#48051] {% comment %}doc{% endcomment %}

The server CLI commands (start, start-single-node, demo) now support a new flag named --redactable-logs, which introduces markers in generated log entries to facilitate redaction of sensitive information by cockroach debug zip and other CockroachDB APIs. This is an experimental feature currently not enabled by default, but is recommended for all deployments and will be enabled by default in a later version. Note: the flag is advertised (in --help) by cockroach start and cockroach start-single-node, where log files are expected as a matter of course; it is also supported, yet hidden (from --help), by every other CLI command because every command can also produce log entries when passed --log-dir or --logtostderr. [#48051][#48051] {% comment %}doc{% endcomment %}

Advanced troubleshooting information (such as internal details from the Go runtime) is now saved in a separate log file named <program>-stderr.xxx.log in the configured log directory. [#48051][#48051] {% comment %}doc{% endcomment %}

[jseldess]

Closing in favor of #7490.