Fixes #18438 - control notifications polling

refs #19317 - move FiltersHelperOverrides to app/registries/

Uses class to hold state, should be kept in the autoload_once registry
directory.

fixes #19464 - rewrite Dashboard::Manager to support autoloading

Replaces class-level widget storage with a static list of built-in
widgets, then appends the registered plugin widgets to get the full
default list of widgets. As a result, the class can safely be reloaded...

Fixes #19399 - Allow API to show usernames with periods

fixes #19317, #10927 - move registries to autoload_once path

Partially reverts 70ce8fe to reinstate autoload_once_paths as the
preferred way to load registry-type objects with class variables
containing data set up during app initialisation (e.g. plugin
registrations, menu items.)...

fixes #19192 - adds mark all as read notification action

This implements missing feature from patternfly ( see http://www.patternfly.org/pattern-library/communication/notification-drawer/#/code/angular)

Fixes #17588 - Remove 1.16 deprecations

show_taxonomy_tabs helper, Settings.method helper and email.yaml support

Refs #13772 - ensure ApplicationRecord is loaded soon enough

In `lib/core_extensions.rb` we define as `per_page` method, that gets
called by `will_paginate` at load time of the models. The issue is
we are using `Setting` model there, that inherits from the...

fixes #18445 - always define eager_load_paths, use require_dep

Allows `eager_load!` to be called or enabled in any environment without
loading files under lib/ twice. Switches many `require` calls to Rails'
`require_dependency` to always use its dependency loader, so when eager...

Revert "Revert "fixes #18691 - add as_deprecation_tracker to test environment""

This reverts commit 5a4fdbf71decfb26b88b139bf1f0136d3d3189d4.