Get rid of legacy admin widget support.
Review Request #12108 — Created March 7, 2022 and submitted
This change ports our two remaining legacy widgets (server cache and
activity graph) to inherit from
BaseAdminWidgetinstead of the old
Widgetclass, and then removes support for the legacy mode.
The server activity graph has additionally been ported to use the new JS
model/view architecture. As part of this, I've modernized the code a bit
but haven't spent any time redesigning the functionality or look.
Loaded the admin site and interacted with the widgets.
Revision 2 (+884 -1190)