Add APIs to help extract rules from a set of rules based on unique subject and subject type

This task is about implementing new APIs to help :

• Extract rules whose subject is a user or a group, the returned rules are normalized (see RIGHTSAPI-20)
• Organize a set of rules based on subject reference and rule state (Allow/Deny)

The following APIs will be added :

• List<ReadableSecurityRule> getUserRulesNormalized(List<ReadableSecurityRule> rules) : Extract rules whose subject is a user from a set of rules. Returned rules are normalized.
• List<ReadableSecurityRule> getGroupRulesNormalized(List<ReadableSecurityRule> rules) : Extract rules whose subject is a group from a set of rules. Returned rules are normalized.
• Map<DocumentReference, Pair<ReadableSecurityRule, ReadableSecurityRule>> organizeRulesBySubjectAndState(
  List<ReadableSecurityRule> rules) : Organize a set of rules based on subject reference and rule state (Allow/Deny).