os-bind: Add support for additional RPZ files and/or new addition to the blocklist

[ajkblue]

• [x] I have read the contributing guide lines at https://github.com/opnsense/plugins/blob/master/CONTRIBUTING.md
• [x] I have searched the existing issues, open and closed, and I'm convinced that mine is new.
• [x] When the request is meant for an existing plugin, I've added its name to the title.

Is your feature request related to a problem? Please describe. I cannot add custom RPZ files to the BIND DNSBL list.

Describe the solution you'd like It would be convenient to add a custom RPZ file to the BIND plugin, such as the way that Unbound has an option to add custom blocklists at https://x.x.x.x/ui/unbound/dnsbl/index after ticking the "advanced mode" switch. For example, there is a DOH blocklist in RPZ format that would be very useful located at jpgpi250/piholemanual/DOH.rpz.

Describe alternatives you've considered If it is not as easy to add a custom URL box to the BIND plugin page due to different file formates (e.g., this file is ready as a .rpz file, not formatted as a regular domain list in .txt file like the others), then this is an additional blocklist that could be considered as part of the default BIND blocklists.

[boomer41]

Additionally, could we add an option to add a local DNS zone as a RPZ list? Currently, I have a use case: The RPZ zone gets synchronized to OPNsense as a secondary zone via DNS transfers. In BIND, i just need to set this domain as a RPZ zone. However, I can only use some of the preselected blocklists of the plugin.

[OPNsense-bot]

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