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>

routers/web/web.go

@@ -323,6 +323,7 @@ func RegisterRoutes(m *web.Route) {
 		m.Group("/appearance", func() {
 			m.Get("", user_setting.Appearance)
 			m.Post("/language", bindIgnErr(forms.UpdateLanguageForm{}), user_setting.UpdateUserLang)
+			m.Post("/hidden_comments", user_setting.UpdateUserHiddenComments)
 			m.Post("/theme", bindIgnErr(forms.UpdateThemeForm{}), user_setting.UpdateUIThemePost)
 		})
 		m.Group("/security", func() {