Rollout launcher mode to 5% of users (#2914)

### Motivation

We've been using the new launcher mode for the server for a few weeks now, with zero issues encountered so far.

Let's roll it out to 5% of users. A larger group of users will help surface any other errors in our telemetry.

### Implementation

Instead of having a setting dedicated to the launcher, I just made it a feature flag, which is what we should do going forward.

vscode/package.json

@@ -473,11 +473,6 @@
           "type": "boolean",
           "default": true
         },
-        "rubyLsp.useLauncher": {
-          "description": "[EXPERIMENTAL] Uses server launcher for gracefully handling missing dependencies.",
-          "type": "boolean",
-          "default": false
-        },
         "rubyLsp.featureFlags": {
           "description": "Allows opting in or out of feature flags",
           "type": "object",
@@ -489,6 +484,10 @@
             "tapiocaAddon": {
               "description": "Opt-in/out of the Tapioca add-on",
               "type": "boolean"
+            },
+            "launcher": {
+              "description": "Opt-in/out of the new launcher mode",
+              "type": "boolean"
             }
           },
           "default": {}

vscode/src/client.ts

@@ -69,7 +69,6 @@ function getLspExecutables(
   const customBundleGemfile: string = config.get("bundleGemfile")!;
   const useBundlerCompose: boolean = config.get("useBundlerCompose")!;
   const bypassTypechecker: boolean = config.get("bypassTypechecker")!;
-  const useLauncher: boolean = config.get("useLauncher")!;
 
   const executableOptions: ExecutableOptions = {
     cwd: workspaceFolder.uri.fsPath,
@@ -112,7 +111,7 @@ function getLspExecutables(
       args.push("--branch", branch);
     }
 
-    if (useLauncher) {
+    if (featureEnabled("launcher")) {
       args.push("--use-launcher");
     }
 

vscode/src/common.ts

@@ -80,6 +80,7 @@ export const SUPPORTED_LANGUAGE_IDS = ["ruby", "erb"];
 // Note: names added here should also be added to the `rubyLsp.optedOutFeatureFlags` enum in the `package.json` file
 export const FEATURE_FLAGS = {
   tapiocaAddon: 0.0,
+  launcher: 0.05,
 };
 
 type FeatureFlagConfigurationKey = keyof typeof FEATURE_FLAGS | "all";