Promote 'New identity' button as a primary action

What does this MR do and why?

• remove New identity from the user identity table (identity tab) and add it to the primary action buttons row
• move left the Edit and User administration to the left
• add pencil-square icon to the Edit button
• remove ellipsis icon from the User administration

Part of #294608 (closed)

Screenshots or screen recordings

Current

Proposed

Implemented

Note: I have removed the primary variant from the Confirm user button, so only one button has a primary status.

How to set up and validate locally

1. Login as an admin
2. Go to one of the user, for example: https://localhost:3000/admin/users/randy/identities

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.