admin-analytics: make user management enabled by default

Created by: erzhtor

This PR:

• Make user management enabled by default
• Add tooltips to legend formatted numbers
• Remove the "Total users" value

Test plan

• sg start
• open http://localhost:3080/site-admin/users
  • Check that the NEW user management is rendered
• Open http://localhost:3080/site-admin/users?feature-flag-key=user-management-disabled&feature-flag-value=true
  • Check that the OLD user management is rendered

App preview:

• Web
• Storybook

Check out the client app preview documentation to learn more.