New observable role enum
This replaces uses of SES_OBSERVABLE_ROLE_MAPPING with a new RBA_OBSERVABLE_ROLE_MAPPING for splunkd content (left SSA alone for now)- this new enum is a subset of the old one, only allowing for two possible values. I've modified the existing validator to use this, as well as an additional validation that limits tags.observable[].role to a length of 1. So now, every observable will be either an Attacker (threat object), or a Victim (risk object), and we can begin to transition to a new rba object.
Content changes because of this change, including updates to deprecated detections, are in this PR: https://github.com/splunk/security_content/pull/3061
I've also updated the templated detection to reflect this new behavior. Smoketest jobs will fail until the linked security_content PR is merged.