Refactor hiding-methods, remove jQuery show/hide, remove .hide class, remove inline style=display:none (#22950)

Close #22847

This PR:

* introduce Gitea's own `showElem` and related functions
* remove jQuery show/hide
* remove .hide class
* remove inline style=display:none 

From now on:

do not use:
* "[hidden]" attribute: it's too weak, can not be applied to an element
with "display: flex"
* ".hidden" class: it has been polluted by Fomantic UI in many cases
* inline style="display: none": it's difficult to tweak
* jQuery's show/hide/toggle: it can not show/hide elements with
"display: xxx !important"

only use:
* this ".gt-hidden" class
* showElem/hideElem/toggleElem functions in "utils/dom.js"

cc: @silverwind , this is the all-in-one PR

web_src/js/features/repo-release.js

@@ -3,13 +3,14 @@ import {attachTribute} from './tribute.js';
 import {initCompMarkupContentPreviewTab} from './comp/MarkupContentPreview.js';
 import {initEasyMDEImagePaste} from './comp/ImagePaste.js';
 import {createCommentEasyMDE} from './comp/EasyMDE.js';
+import {hideElem} from '../utils/dom.js';
 
 export function initRepoRelease() {
   $(document).on('click', '.remove-rel-attach', function() {
     const uuid = $(this).data('uuid');
     const id = $(this).data('id');
     $(`input[name='attachment-del-${uuid}']`).attr('value', true);
-    $(`#attachment-${id}`).hide();
+    hideElem($(`#attachment-${id}`));
   });
 }