Fix the key used for extraction of delegate debug handle map in emitter (#493)

Summary:
Pull Request resolved: #493

In D49173918 while looking for the delegate map in the lowered_module metadata i ended up using the wrong key. It should be `debug_handle_map` and not `delegate_map`.

Reviewed By: Jack-Khuu

Differential Revision: D49620440

fbshipit-source-id: 473a6eb98dec712a45bf4b916397d6ccba2868eb

Author: tarun292

exir/emit/_emitter.py

@@ -950,7 +950,7 @@ def _add_delegate_map(
         """
         delegate_map = {}
         if hasattr(lowered_module, "meta"):
-            delegate_map = lowered_module.meta.get("delegate_map", {})
+            delegate_map = lowered_module.meta.get("debug_handle_map", {})
 
         self.instr_id_to_delegate_debug_id_map[delegate_instruction_id] = {
             "name": lowered_module.backend_id,

exir/emit/test/test_emit.py

@@ -1324,4 +1324,16 @@ def forward(self, x, y):
             .to_edge()
             .to_executorch()
         )
+        # Reading the program triggers the call to emit_program underneath which
+        # we need to be done for our test to succeed.
+        exec_prog.program
         self.assertIsNotNone(exec_prog.delegate_map)
+        self.assertIsNotNone(exec_prog.delegate_map.get("forward"))
+        self.assertIsNotNone(exec_prog.delegate_map.get("forward").get(0))
+        self.assertEqual(
+            exec_prog.delegate_map.get("forward").get(0).get("name"),
+            "BackendWithCompilerDemo",
+        )
+        self.assertTrue(
+            len(exec_prog.delegate_map.get("forward").get(0).get("delegate_map")) != 0
+        )