Desktop: Fixes #10023: Beta editor plugins: Fix opening and closing settings can break some plugins with legacy code

[personalizedrefrigerator]

Summary

This fixes an issue where opening and closing settings could break some legacy plugins. A similar change was also made as a part of #9928.

Fixes #10023.

Testing

Follow reproduction steps in #10023:

1. Apply the following diff:

diff --git a/packages/app-cli/tests/support/plugins/codemirror6/src/contentScript.ts b/packages/app-cli/tests/support/plugins/codemirror6/src/contentScript.ts
index af0532dcf..3a816a16c 100644
--- a/packages/app-cli/tests/support/plugins/codemirror6/src/contentScript.ts
+++ b/packages/app-cli/tests/support/plugins/codemirror6/src/contentScript.ts
@@ -47,7 +47,7 @@ export default (_context: ContentScriptContext): CodeMirrorContentScriptModule =
 
 			// We can also register editor commands. These commands can be later executed with:
 			//   joplin.commands.execute('editor.execCommand', { name: 'name-here', args: [] })
-			codeMirrorWrapper.registerCommand('wrap-selection-with-tag', (tagName: string) => {
+			(codeMirrorWrapper as any).defineExtension('wrap-selection-with-tag', (tagName: string) => {
 				const editor: EditorView = codeMirrorWrapper.editor;
 
 				// See https://codemirror.net/examples/change/

2. Build and add the CodeMirror 6 demo plugin (packages/app-cli/tests/support/plugins/codemirror6/) as a development plugin.
3. Verify that running :underline from the command palette works.
4. Open settings
5. Close settings
6. Verify that running :underline from the command palette still works.

This has been tested successfully on Ubuntu 23.10.