Goal of this change is to simplify usage of the watch page feature.
It comes with important changes:
   - the watch location switches in the bell menu area have been removed
   - a new button with a logo and a status has been introduced next to edit button
   - a new modal has been introduced when clicking on the button providing various choices
   - the watch page API have been modified to not just provide boolean value watch / not watched, but to provide a larger panel of possible statuses
   - a REST resource have been provided to allow watching / blocking / removing a filter on a location
  

* Start providing REST API for watch pages to simplify operations
  * Distinguish more cases for watched / ignored pages to improve UI
  * Provide implementation for REST API for watching pages
  * Improve WatchEntitiesManager API to support more operations
  * Improve WatchedEntityReference API to use UserReference
  * Provide a dedicated page to handle watch settings
  * Start writing javascript code to handle choices
  * Fix issue in WatchedEntitiesManager
  * Start providing doc / fixing checkstyle
  * Handle a bit more actions in UI
  * Fix a bug in state computer related to the fact that the scoe filter
    hierarchy is not really a hierarchy
  * Provide a new API to allow computing the reference of the immediate
    ancestor of a page for which a filter exists
  * Improve UI to base possible actions on multiple criteria: current
    watch status, presence or not of a filter on an ancestor, and check
if the page is terminal or not
  * Encode all options for the watch settings modal
  * Change the URL scheme for the REST API
  * Minor improvments
  * Provide test for notification rest module
  * Fix checkstyle
  * Put revapi ignores
  * Start fixing since
  * Provide translations and improve UIX code
  * Provide page object and fix integration tests
  * Ensure to not display the watch status for guest
  * Fix a few since and some problems in UIX
  * Fix API of WatchedUserReference
  * Fix bad escaping
  * Better exception handling for creating references
  * Various improvments in translations (active voice + use of ignore)
  * Improve a bit the UI
  * Improve UI when a page is ignored/followed by an ancestor and check
    proper rights
  * Review available options and improve javascript to allow chaining
    operations: following space when the page is followed implies to
first unfollow the page to not keep unnecessary filters and mess up the
UI
  * Improve translations
  * Clean up some unnecessary code
  * Make the UI a bit more clear
  * Fix some stuff after rebsae
  * Slightly improve UX
  * Fix missing unstable
  * Fix bad deprecated API call

  * Deprecate and legacify NotificationFilterPreferenceProvider and
    NotificationFilterPreference#getProviderHint
  * Clean up all code relying on it simplifying a lot the implem of
    NotificationFilterPreference
  * Only valid usage of the providerHint was for checking if a filter
    preference was stored or not: replaced it with checking the ID of
the filter
  * Fix bad prefix in filters internal ids
  * Fix typos

* Add revapi ignore since there's no real breakage according to https://revapi.org/revapi-java/0.28.1/differences.html#java.class.nonFinalClassInheritsFromNewClass

* Add a PinnedChildPages class to hold the list of child pages that should be displayed before the rest of the remaining child pages.
* Store the pinned top level pages on XWikiPreferences and the pinned child pages for a nested page on its WebPreferences.
* Add a wiki and space administration section to configure the pinned child pages.
* Implement a tree filter that excludes pinned child pages, so that they can be displayed first.
* Add support for grouping tree nodes and refactor the document tree node to use it.
* Implement a picker for pinned child pages (not yet connected to the REST resource, which needs to be implemented)
* Prepare the ground for refactoring the "Children" page REST resource to support the "reference" hierarchy mode, and for adding a wiki "Children" REST resource to get the top level pages.

  * Ensure to use proper WikiReference when resolving user document
    reference
  * Provide some more logs to perform migration of users
  * Move the migration so that it's executed in recent version of XS
  * Put forgotten unstable annotations on migrations

XWIKI-21977 : Module xwiki-platform-legacy-oldcore does not expose the same extension features as xwiki-platform-oldcore

* Move oldcore extension features to a property of xwiki-platform-core
* Re-use property in oldcore and legacy-oldcore modules

XWIKI-12955: Upgrade to JAX-RS 2.1.6 (JSR370)
XWIKI-21709: Upgrade to Jetty Client 10.0.19
XWIKI-12674: Replace Restlet with Jersey

Only part of revapi ignores should have been removed.

This reverts commit aa7e3458.

This reverts commit ee9505d3.

  * Add other missing revapi ignores

XWIKI-21674: Docker tests are cached by the Gradle Cache even when using different environment test properties
* Fix conflicting version of Groovy

* Deduplicate common properties from DocumentInstanceOutputProperties and
  UserInstanceOutputProperties in a common super class.

XWIKI-21674: Docker tests are cached by the Gradle Cache even when using different environment test properties

  * Add missing revapi ignores