Merge #3534

3534: Feature: vscode impl nightlies download and installation r=Veetaha a=Veetaha

I need to test things more, but the core shape of the code is quite well-formed.
The main problem is that we save the release date only for nightlies and there are no means to get the release date of the stable extension (i.e. for this we would need to consult the github releases via a network request, or we would need to somehow save this info into package.json or any other file accessible from the extension code during the deployment step, but this will be very hard I guess).
So there is an invariant that the users can install nightly only from our extension and they can't do it manually, because when installing the nightly `.vsix` we actually save its release date to `globalState`

Closes: #3402

TODO:
- [x] More manual tests and documentation

cc @matklad @lnicola 

Co-authored-by: Veetaha <gerzoh1@gmail.com>
Co-authored-by: Veetaha <veetaha2@gmail.com>

editors/code/src/main.ts

@@ -8,6 +8,7 @@ import { activateHighlighting } from './highlighting';
 import { ensureServerBinary } from './installation/server';
 import { Config } from './config';
 import { log } from './util';
+import { ensureProperExtensionVersion } from './installation/extension';
 
 let ctx: Ctx | undefined;
 
@@ -34,7 +35,13 @@ export async function activate(context: vscode.ExtensionContext) {
 
     const config = new Config(context);
 
-    const serverPath = await ensureServerBinary(config.serverSource);
+    vscode.workspace.onDidChangeConfiguration(() => ensureProperExtensionVersion(config).catch(log.error));
+
+    // Don't await the user response here, otherwise we will block the lsp server bootstrap
+    void ensureProperExtensionVersion(config).catch(log.error);
+
+    const serverPath = await ensureServerBinary(config);
+
     if (serverPath == null) {
         throw new Error(
             "Rust Analyzer Language Server is not available. " +