Add support for pre/post update hooks in the PluginEditCtrl.

This allows users to intercept the update procedure from their own
controller to modify the pluginSettings before they are saved and
perform additional tasks like syncing state via a third party API.

fix(prometheus): fixed templating issue with prometheus for when using variable with non regex operator, #2918

remove forced page header from app pages.

redact settings containing 'secret' besides 'password'

Ensure that settings with the word 'secret' in the name are redacted just
as ones with 'password' in the name are. For example, the Google Auth
client secret should be redacted now.

closes #4206

add supressNav property to plugin pages.

close #4209

- dashlist will only show dashboards from same org
- notfound dashboards will not be added

closes #4207

This allows pages to be registered that dont show up in the
Navigation menu when the App is pinned.

closes #4205