Add IID (Internal-ID) to Feature Flags

As mentioned in this discussion #26456 (comment 224219687), Feature Flags don't currently have an IID field which is necessary to join and visualize Feature Flags with Issues/MRs/Epics #26456 (closed).

Proposal

Add the IID field to Features Flags and show that value on the Feature Flag page

Feature flag edit page

• Add IID to the title when editing
• Remove edit from the title

For new feature flags, display New Feature Flag until saved

Feature flags lists

• Add a column to display IID