Drop fomantic build (#33845)

We would never update or build fomantic again, we have forked it as a
private library long time ago.

So just put the JS and CSS files in "fomantic/build" into git. And use
"import" to use them.

Remove "form.js", rewrite "tab" component.

All source code is from official Fomantic UI build. Will apply patches
in separate PRs.

web_src/js/modules/fomantic/tab.ts

@@ -0,0 +1,19 @@
+import $ from 'jquery';
+import {queryElemSiblings} from '../../utils/dom.ts';
+
+export function initFomanticTab() {
+  $.fn.tab = function (this: any) {
+    for (const elBtn of this) {
+      const tabName = elBtn.getAttribute('data-tab');
+      if (!tabName) continue;
+      elBtn.addEventListener('click', () => {
+        const elTab = document.querySelector(`.ui.tab[data-tab="${tabName}"]`);
+        queryElemSiblings(elTab, `.ui.tab`, (el) => el.classList.remove('active'));
+        queryElemSiblings(elBtn, `[data-tab]`, (el) => el.classList.remove('active'));
+        elBtn.classList.add('active');
+        elTab.classList.add('active');
+      });
+    }
+    return this;
+  };
+}