XWIKI-22271: Custom filters to subwiki remain on the main Wiki after subwiki is deleted (#3219)

  * Iterate over all wikis when deleting filters related to a wiki
  * Fix unit test
  * Provide a migration to clean up filters related to deleted wikis
  * Provide unit test for the migration
  * Fix migration query after testing
  * Add a few comments over the query

(cherry picked from commit 858605a2)

  * Set the proper DB version for 16.4.x branch.
  * Rename the migration class for 16.4.x branch so that it remains consistent with DB version.
  * Rename the migration test too.

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Co-authored-by: Simon Urli <simon.urli@xwiki.com>