[UserCap FE]: Warn group owners when changing User Caps settings about automatically approving users

Description

After implementing #330027 (closed), we need to display a modal warning to group owners if they change settings that could have the side-effect of auto-approving users. The modal will display only if there is the risk of auto-approving users. A similar modal was implemented for Self-Managed: !55509 (merged)

Scenarios to show the modal

Issue	Scenario
#330028 (closed) (👈 you're here)	Group owner adjusts user caps settings (increase or disable)
#334382	Group owner clicks "Approve all" action
#334383	Group owner clicks "Approve" button for single pending user

Feature flag

This feature will be implemented under the saas_user_caps FF

Designs

The design should resemble the one of the modal for Self-Managed: !55509 (merged)

Availability & Testing

Tests should accompany this change:

• Vue frontend spec for checking display of Modal
• Bimodal Feature Flag feature test
  • If Feature flag is enabled: check Modal shows given the appropriate circumstances.
  • If Feature flag is disabled: check Modal does not show.