This commit introduces a little bit of duplication
since the old plugin UIs not using the new plugin show
page look different from ones like AI and Gamification
which have been converted. We can use the new admin
header component on the plugins list, but for the other
pages we are manually rendering a breadcrumb trail and
the list of plugin tabs.
Over time as we convert more plugins to use the new UI
guidelines and show page we can get rid of this duplication.
This commit contains a few improvements:
* Use LinkTo instead of a button with a weird action referencing the
controller to navigate to the filtered settings for a plugin
* Add an AdminPlugin model with tracked properties and use that when
toggling the setting on/off and in the templates
* Make it so the Settings button for a plugin navigates to the correct
site setting category instead of always just going to the generic
"plugins" one if possible
