[Feature Request] Ability to add specific NIST mappings

[ljstella]

Source: https://splunk-usergroups.slack.com/archives/CDNHXVBGS/p1730893006095839

Customers would like to add specific NIST annotations.

In addition to overriding the built in NIST & CIS mappings, in order to take advantage of any unmanaged annotation frameworks customers would want to use, we should likely consider some sort of basic KV pair object under tags to accommodate future requests regarding customizing this.