Rephrase error messages in vulnerability form

The following discussion from !78703 (merged) should be addressed:

Comment from @jeldergl:

@beckalippert the alert isn't excessive, and actually required for error identification. I think what could help would be a little copywriting for the errors below each input. Instead of stating "This field is required." over and over it could be more helpful, like "Enter your name" or "You must select a severity." Page height wouldn't be a factor for showing an alert or not.

Implementation Plan

• Rename error messages for new vulnerability form.