Update the datagrid pages to use the new setupPage JS support.
Review Request #10736 — Created Oct. 2, 2019 and submitted
Review Board 4.0 introduced a new consistent way of setting up page
events of page elements. This change moves all the datagrid pages over
to the new method.
To do this, the base datagrid template now fills in the page template
blocks to specify the model/view classes that the datagrid wants, along
with the attributes and options for those classes. This makes use of new
DataGridJSMixin, which subclasses can override to provide
Tested that all the datagrid pages were still working as expected in mobile
and desktop modes.
Unit tests pass.