LP1965448 Holdings edit enforce required stat cats

LP1965448 Holdings edit enforce required stat cats

Required copy stat cats require a value when creating or editing
copies.

Switching between tabs in the copy editor no longer alert the user when
a change is pending, since it may be necessary to hop between tabs to
resolve issues.  Pending changes alerts will still appear when leaving
the page if needed.

Signed-off-by: Bill Erickson <berickxx@gmail.com>
Signed-off-by: Galen Charlton <gmc@equinoxOLI.org>