This updates all of our actions with custom rendering to instead use the

new renderer support. Most of these just set a default renderer or clear

away rendering state (making use of the renderer from the parent group).

Some implement small specialized custom renderers built for that action.
There's one notable architectural change here. We're now deprecating

is_custom_rendered(), which was introduced in Review Board 7 to

handle menu item actions that managed their own element style rather

than using the default Ink menu item rendering. This wasn't used for

anything else in practice, and isn't very usefully generic. Now, instead

of this function, menu item elements can set

data-custom-rendered="true", and the menu action will make use of its

element.

Unit tests passed.
Tested all the actions we have in the UI, and particularly the different

menu actions, making sure they rendered and were invoked correctly.
Checked to make sure we no longer had any deprecation warnings in the

devserver logs.