chore: Hoist non-generic part out of add_action_internal. (#2981)

add_action_internal shows up often in downstream crates (as it should
be, since it's a generic function it's codegened in each crate that uses
it); it adds non-trivial amounts of LLVM IR to the build as a whole
which we can cut down a bit by doing the inner fn trick.

Release Notes:

- N/A

crates/gpui/src/app.rs

@@ -684,24 +684,42 @@ impl AppContext {
                 );
             },
         );
-
-        self.action_deserializers
-            .entry(A::qualified_name())
-            .or_insert((TypeId::of::<A>(), A::from_json_str));
+        fn inner(
+            this: &mut AppContext,
+            name: &'static str,
+            deserializer: fn(serde_json::Value) -> anyhow::Result<Box<dyn Action>>,
+            action_id: TypeId,
+            view_id: TypeId,
+            handler: Box<ActionCallback>,
+            capture: bool,
+        ) {
+            this.action_deserializers
+                .entry(name)
+                .or_insert((action_id.clone(), deserializer));
 
             let actions = if capture {
-            &mut self.capture_actions
+                &mut this.capture_actions
             } else {
-            &mut self.actions
+                &mut this.actions
             };
 
             actions
-            .entry(TypeId::of::<V>())
+                .entry(view_id)
                 .or_default()
-            .entry(TypeId::of::<A>())
+                .entry(action_id)
                 .or_default()
                 .push(handler);
         }
+        inner(
+            self,
+            A::qualified_name(),
+            A::from_json_str,
+            TypeId::of::<A>(),
+            TypeId::of::<V>(),
+            handler,
+            capture,
+        );
+    }
 
     pub fn add_async_action<A, V, F>(&mut self, mut handler: F)
     where