Refactored nb-arrow to use stylobate

This PR is the refactoring of `nb-arrow` to use the stylobate's implementation of arrow. Also, some minor things were fixed in the process (better hit area for service-arrow link, linkless service-arrow, arrow should now work in IE (need testing though), “requests” placeholder now uses nb-input's `hint` etc.)

As this PR changes a lot of things around the arrow, it should be tested and reviewed with care.