Load admin monitors popup content via ajax (#5063)

* Admin monitors popup is now loaded through an API

* Fixes form submission inside the popup

- Wraps it in an l:ajax template so that proper variables are set
- Applies the csrf crumbs to the forms after the popup is constructed

* Handle authorization and empty state

* Apply suggestions from code review

Co-authored-by: Tim Jacomb <timjacomb1+github@gmail.com>

* Fix JS error where there were monitors of only one kind

* Revert changes to indentation of inline JS

* Clarify ESC keyCode with a comment

* Update core/src/main/resources/jenkins/management/AdministrativeMonitorsDecorator/resources.js

Co-authored-by: Tim Jacomb <timjacomb1+github@gmail.com>

* Multiple small adjustments

- Remove unused imports
- Remove non-necessary call for the response that are set in the getView
- Keep the previous improvement about limiting the number of call to getMonitorList()

Co-authored-by: Tim Jacomb <timjacomb1+github@gmail.com>
Co-authored-by: Wadeck Follonier <wadeck.follonier@gmail.com>