Improve markdown editor: width, height, preferred (#23895)

Follow #23876


1. Fine tune the heights of the editors (like before)
    * Auto expand the editor (increase/decrease the height) when editing
2. Remember user's last used editor (textarea/easymde) in LocalStorage,
then next time the editor will be switched automatically
* No need to introduce extra config option, it satisfies all users,
including who prefer EasyMDE
3. Also fix the width problem of Review Panel

Screenshot:

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![image](https://user-images.githubusercontent.com/2114189/229518585-2e05827e-8355-48f3-a20c-2c8b9e60ce74.png)


![image](https://user-images.githubusercontent.com/2114189/229518173-4caa6da7-6ad9-40e9-bf1a-ceddfcd4b37f.png)


![image](https://user-images.githubusercontent.com/2114189/229507886-148e9b84-9b58-46d1-ba3f-727e1396f476.png)


![image](https://user-images.githubusercontent.com/2114189/229518258-9f522294-1e64-4b06-91ab-ab43b0353aaa.png)


![image](https://user-images.githubusercontent.com/2114189/229507752-6d540ac7-7748-4bb6-bc09-28acab32d31b.png)


![image](https://user-images.githubusercontent.com/2114189/229510899-de322af5-57e8-4dc5-9a61-771a3b1bee79.png)


</details>

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Co-authored-by: silverwind <me@silverwind.io>

web_src/js/features/repo-wiki.js

@@ -44,6 +44,11 @@ async function initRepoWikiFormEditor() {
   renderEasyMDEPreview();
 
   editor = await initComboMarkdownEditor($editorContainer, {
+    useScene: 'wiki',
+    // EasyMDE has some problems of height definition, it has inline style height 300px by default, so we also use inline styles to override it.
+    // And another benefit is that we only need to write the style once for both editors.
+    // TODO: Move height style to CSS after EasyMDE removal.
+    editorHeights: {minHeight: '300px', height: 'calc(100vh - 600px)'},
     previewMode: 'gfm',
     previewWiki: true,
     easyMDEOptions: {