hba: stricter parsing and better pretty-printing

[jseldess]

Jesse Seldess commented:

PR: cockroachdb/cockroach#43811

From release notes:

CockroachDB now properly rejects control characters in the value of the server.host_based_authentication.configuration [cluster setting](../v20.1/cluster-settings.html]. Previously, these characters were accepted and would silently result in unintended rule matching. Deployments careful to strip control characters from their HBA configurations are not affected. [#43811][#43811) {% comment %}doc{% endcomment %}

Jira Issue: DOC-434