refactor: clean up legacy templates and js (#39808)

* Remove unused `"root"` data attributes from templates
* Use our "confirmModal" as much as possible (partially for #39643)
* Use "data-global-init" to refactor a lot of legacy code
* Refactor and clearify initRepoIssueCommentDelete's behavior to help #36862
* Remove dead code `common-organization.ts`

web_src/css/repo.css

@@ -620,10 +620,6 @@
   min-width: 0;
 }
 
-.repository .comment.form .content .field:first-child {
-  clear: none;
-}
-
 .repository.new.milestone textarea {
   height: 200px;
 }