Add config options to hide issue events (#17414)

* Add config option to hide issue events
Adds a config option `HIDE_ISSUE_EVENTS` to hide most issue events (changed labels, milestones, projects...) on the issue detail page.
If this is true, only the following events (comment types) are shown:
* plain comments
* closed/reopned/merged
* reviews

* Make configurable using a list

* Add docs

* Add missing newline

* Fix merge issues

* Allow changes per user settings

* Fix lint

* Rm old docs

* Apply suggestions from code review

* Use bitsets

* Rm comment

* fmt

* Fix lint

* Use variable/constant to provide key

* fmt

* fix lint

* refactor

* Add a prefix for user setting key

* Add license comment

* Add license comment

* Update services/forms/user_form_hidden_comments.go

Co-authored-by: Gusted <williamzijl7@hotmail.com>

* check len == 0

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Gusted <williamzijl7@hotmail.com>
Co-authored-by: 6543 <6543@obermui.de>

services/mailer/mail.go

@@ -449,7 +449,7 @@ func actionToTemplate(issue *models.Issue, actionType models.ActionType,
 			name = "code"
 		case models.CommentTypeAssignees:
 			name = "assigned"
-		case models.CommentTypePullPush:
+		case models.CommentTypePullRequestPush:
 			name = "push"
 		default:
 			name = "default"

services/mailer/mail_comment.go

@@ -21,7 +21,7 @@ func MailParticipantsComment(ctx context.Context, c *models.Comment, opType mode
 	}
 
 	content := c.Content
-	if c.Type == models.CommentTypePullPush {
+	if c.Type == models.CommentTypePullRequestPush {
 		content = ""
 	}
 	if err := mailIssueCommentToParticipants(