Revert "debugger: Remove feature flag"

This reverts commit 82dfa82ba7.

crates/feature_flags/src/feature_flags.rs

@@ -77,6 +77,11 @@ impl FeatureFlag for NotebookFeatureFlag {
     const NAME: &'static str = "notebooks";
 }
 
+pub struct DebuggerFeatureFlag {}
+impl FeatureFlag for DebuggerFeatureFlag {
+    const NAME: &'static str = "debugger";
+}
+
 pub struct ThreadAutoCaptureFeatureFlag {}
 impl FeatureFlag for ThreadAutoCaptureFeatureFlag {
     const NAME: &'static str = "thread-auto-capture";