Improve the email input experience within the invite modal

Summary

Driving team member invites is a key focus area for Growth. While reviewing the current UX within the invite modal, we identified some subpar behaviours specific to the email input/capture

Relates to Q4 KR: https://gitlab.com/gitlab-com/gitlab-OKRs/-/work_items/5396

Notes from @jhalloran - The standard UX for adding emails is to tab and it will automatically select this input. It's not clear that you need to select the gray drop down here. (I'm also not 100% sure if this is meeting accessibility standards) The error state is also not helpful because to me it looks like I did correctly add an email and I wasn't sure why it wasn't proceeding

Adding email	Error

MVC solutions to investigate with engineering

Attempt to implement the below or explain why they can't be implemented

1. Using the tab key after inputing an email into the form field should "select" the email the same way as clicking on the grey "Invite [email address] by email" box currently does. This is a very common UX pattern we should be utilizing.
2. Update the form field title to "Username, name or email address"