Update definitions to use feature_category

Follow up from discussion &8383 (comment 1158471791) and !100024 (comment 1133728812)

The one suggestion I'll add, unrelated to this MR, instead of using group, use feature_category. Feature categories map directly to groups, but groups are more likely to change. Say, using this example, project management was split into two groups, one focused on team planning, and one focused on planning analyitcs, we'd probably want this to stay with the group assigned team planning. If we have the group designation in here, that's one more thing that has to be updated if groups change.

https://about.gitlab.com/handbook/product/categories/#categories-a-z

We use this same tactic for categorizing usage data, database tables, and api endpoints.

Implementation Plan

1. Update config/audit_events/types/type_schema.json and replace the group field with feature_category. Update the RSpecs for the schema.
2. Update all the existing YML definitions inside the directories config/audit_events/types and ee/config/audit_events/types and replace group with an appropriate feature_category, we'll probably have to ask the respective groups to suggest the correct feature category for that particular audit event type.
3. Update the bin/audit-event CLI to ask for feature_category as the input instead of group. Update RSpecs for the CLI.