Fine tune more downdrop settings, use SVG for labels, improve Repo Topic Edit form (#23626)

Although it seems that some different purposes are mixed in this PR,
however, they are all related, and can be tested together, so I put them
together to save everyone's time.

Diff: `+79 −84`, everything becomes much better.

### Improve the dropdown settings.

Move all fomantic-init related code into our `fomantic.js`

Fine-tune some dropdown global settings, see the comments.

Also help to fix the first problem in #23625 , cc: @yp05327 

The "language" menu has been simplified, and it works with small-height
window better.

### Use SVG instead of `<i class="delete icon">`

It's also done by `$.fn.dropdown.settings.templates.label` , cc:
@silverwind

### Remove incorrect `tabable` CSS class

It doesn't have CSS styles, and it was only in Vue. So it's totally
unnecessary, remove it by the way.

### Improve the Repo Topic Edit form

* Simplify the code
* Add a "Cancel" button
* Align elements

Before:

<details>

![image](https://user-images.githubusercontent.com/2114189/223325782-f09532de-0c38-4742-ba86-ed35cc9a858d.png)

</details>

After:

![image](https://user-images.githubusercontent.com/2114189/226796347-207feb0a-b3cd-4820-8a3e-01930bab1069.png)

web_src/js/components/DashboardRepoList.vue

@@ -1,6 +1,6 @@
 <template>
   <div>
-    <div v-if="!isOrganization" class="ui two item tabable menu">
+    <div v-if="!isOrganization" class="ui two item menu">
       <a :class="{item: true, active: tab === 'repos'}" @click="changeTab('repos')">{{ textRepository }}</a>
       <a :class="{item: true, active: tab === 'organizations'}" @click="changeTab('organizations')">{{ textOrganization }}</a>
     </div>