Migrate gt-hidden to tw-hidden (#30046)

We have to define this one in helpers.css because tailwind only
generates a single class but certain things rely on this being
double-class. Command ran:

```sh
perl -p -i -e 's#gt-hidden#tw-hidden#g' web_src/js/**/* templates/**/* models/**/* web_src/css/**/*

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
(cherry picked from commit ec3d467f15a683b305ac165c3eba6683628dcb25)

Conflicts:
	templates/install.tmpl
	templates/repo/diff/conversation.tmpl
	templates/repo/issue/view_content/conversation.tmpl
	templates/repo/issue/view_content/sidebar.tmpl
	templates/repo/issue/view_title.tmpl

	resolved by prefering Forgejo version and applying the
	commands to all files

web_src/js/svg.js

@@ -213,7 +213,7 @@ export const SvgIcon = {
       classes.push(...this.className.split(/\s+/).filter(Boolean));
     }
     if (this.symbolId) {
-      classes.push('gt-hidden', 'svg-symbol-container');
+      classes.push('tw-hidden', 'svg-symbol-container');
       svgInnerHtml = `<symbol id="${this.symbolId}" viewBox="${attrs['^viewBox']}">${svgInnerHtml}</symbol>`;
     }
     // create VNode