Add user blocking (#29028)

Fixes #17453

This PR adds the abbility to block a user from a personal account or
organization to restrict how the blocked user can interact with the
blocker. The docs explain what's the consequence of blocking a user.

Screenshots:


![grafik](https://github.com/go-gitea/gitea/assets/1666336/4ed884f3-e06a-4862-afd3-3b8aa2488dc6)


![grafik](https://github.com/go-gitea/gitea/assets/1666336/ae6d4981-f252-4f50-a429-04f0f9f1cdf1)


![grafik](https://github.com/go-gitea/gitea/assets/1666336/ca153599-5b0f-4b4a-90fe-18bdfd6f0b6b)

---------

Co-authored-by: Lauris BH <lauris@nix.lv>

models/fixtures/repository.yml

@@ -614,8 +614,8 @@
   owner_name: user16
   lower_name: big_test_public_3
   name: big_test_public_3
-  num_watches: 0
-  num_stars: 0
+  num_watches: 1
+  num_stars: 1
   num_forks: 0
   num_issues: 0
   num_closed_issues: 0
@@ -945,8 +945,8 @@
   owner_name: org3
   lower_name: repo21
   name: repo21
-  num_watches: 0
-  num_stars: 0
+  num_watches: 1
+  num_stars: 1
   num_forks: 0
   num_issues: 2
   num_closed_issues: 0