XWIKI-18600: Refactor the security modules organization, add a Security Config component and improve some templates

- Introduces the icon extension rest api and default implementation modules
- Introduces the icon extension docker tests module
- Introduces a hasIcon method in IconManager and IconSet to check if a given name exists in an icon set

[Misc] Replace the zip flamingo resource artifact by a jar one so that we can write integration tests for templates in the flamingo skin

[Misc] Split xwiki-platform-web into 2 modules: xwiki-platform-web-templates and xwiki-platform-web-war. Rationale: be able to write integration tests for templates more easily (by depending on the new template module rather than having to unpack the WAR, and use a modified velocity engine to read templates from local files)

XCOMMONS-2094: xwiki-commons-xml cannot be used anymore without adding a custom repository in the settings.xml

  * Add a dependency to URLSearchParam polyfill as a webjar.

  * Change dependencies to rely on commons-job-api where needed
  * Put a dependency to commons-job-default in the minimal war and in
    the tool-packager-plugin

  * Migrate platform-model to platform-model-api and create
    platform-model as a pom module
  * Migrate platform-legacy-model to platform-legacy-model-api to be
    consistent
  * Migrate platform-name-dependencies module to platform-model-validation next to platform-model-api

  * Create components to allow various name strategies.
  * Define two strategies to replace characters or to use slug names (no
    accent, no special characters)
  * Define Administration page to allow choosing the strategy and the
    characters to replace with their replacement
  * Define a script service and template to allow performing name page
    transformation
  * Use this name page transformation URL in the location picker
  * Use the name page validation in CreateAction and in SaveAction in
    case of new pages.

* more accurate scope

* improve the Velocity setup in the context of the XWiki WAR

  * Refactoring of merge implementations to rely on a dedicated
component and to be able to record properly the conflicts.
  * Start the implementation of a conflict decision manager to record
the decision taken on the conflicts.