Add override keyword in codebase (#120755)

For #120675

This uses a script to add the override keyword to places that need it in the codebase

Note that we can't enable the --noImplicitOverride setting yet since there are still around 200 errors that require further attention

src/vs/workbench/api/browser/mainThreadTesting.ts

@@ -152,7 +152,7 @@ export class MainThreadTesting extends Disposable implements MainThreadTestingSh
 		return result.id;
 	}
 
-	public dispose() {
+	public override dispose() {
 		super.dispose();
 		for (const subscription of this.testSubscriptions.values()) {
 			subscription.dispose();