Place block should also allow to filter by category

The Needs Review Queue Bot → tested this issue. It either no longer applies to Drupal core, or fails the Drupal core commit checks. Therefore, this issue status is now "Needs work".

Apart from a re-roll or rebase, this issue may need more work to address feedback in the issue or MR comments. To progress an issue, incorporate this feedback as part of the process of updating the issue. This helps other contributors to know what is outstanding.

Consult the Drupal Contributor Guide → to find step-by-step guides for working with issues.

capysara → changed the visibility of the branch 11.x to hidden.

capysara → changed the visibility of the branch 711735-block-filter-category-11 to hidden.

I updated the MR so it's against 11.x. It works, but the code is just copy/pasted so it needs to be updated for modern coding standards. IS still needs updated as noted in a previous commit.