* fix: hide discussion xblock for openedx provider
* fix: test cases
* refactor: hide xblock is provider not legacy and add message in studio
* fix: lint issue
* refactor: update discussion block studio msg
* fix: test discussion xblock query number
JIRA: https://openedx.atlassian.net/browse/BOM-2580
This PR aims at refactoring the discussion xblock sub project and moving it within the xmodule directory effectively removing its position as a sub project within edx-platform