Add transition between invite members modals

What does this MR do and why?

Smooth transition between initial invite members modal and overage confirmation.

Mind that the state of the input is safe between transitions but not on modal close.

Related to #348486 (closed)

Step	Status
Introduce a FF and a modal on FE	!79644 (merged)
Add smooth transition	👉 you are here
Add logic to when we show overage modal and calculate the amount of users for overage	!78287 (merged) workflowin dev

Mind that the branch is targeting not a master branch till the initial !79644 (merged) MR is merged

Screenshots or screen recordings

Transition

How to set up and validate locally

1. If the feature flag is not enabled user won't see an overage modal

2. Enable the overage modal

   Feature.enable(:overage_members_modal)

3. Visit any group page, then Group Information -> Members http://localhost:3000/groups/<your-group>/-/group_members.

4. Click the Invite members button

5. Add a user and click Invite.

6. Check the modal.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.