rel_3_11 - look at button types in Angular

[Galen Charlton]

Bug 2049780 describes an issue caused by a <button> element in the Angular staff interface not having a type set and thus defaulting to "submit" - which in turn caused a form to not submit when the enter key was sent but instead toggle another button on the form.

There's a patch available for that particular bug, but in general rel_3_11 should be looked at to see if there are other cases lurking where the button type should be explicitly set.

This is an issue only for 3.11.x (and before), as the patches for bug 1850473 took care of the issue in main and rel_3_11. Alas, the button type one from that patch series doesn't apply cleanly, but would be a good starting point.