* [VAULT-35871] UI: Address design UI feedback on namespace picker
* remove unused css class
* dynamic width based on namespace length; not help messages
* handle long namespace name - truncate the second line
* hide/show message element so that it doesn't affect the layout while getting the width.
* add copyright header to scss file
* address PR comments & additional design feedback
* fix syntax error
* address more design feedback: use small buttons
