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>

services/user/user_test.go

@@ -41,7 +41,8 @@ func TestDeleteUser(t *testing.T) {
 		orgUsers := make([]*organization.OrgUser, 0, 10)
 		assert.NoError(t, db.GetEngine(db.DefaultContext).Find(&orgUsers, &organization.OrgUser{UID: userID}))
 		for _, orgUser := range orgUsers {
-			if err := models.RemoveOrgUser(db.DefaultContext, orgUser.OrgID, orgUser.UID); err != nil {
+			org := unittest.AssertExistsAndLoadBean(t, &organization.Organization{ID: orgUser.OrgID})
+			if err := models.RemoveOrgUser(db.DefaultContext, org, user); err != nil {
 				assert.True(t, organization.IsErrLastOrgOwner(err))
 				return
 			}