[lldb] Merge TestSBCommandReturnObject tests

In #125132, Michael pointed out that there are now two tests with the
same name:

./lldb/test/API/api/command-return-object/TestSBCommandReturnObject.py
./lldb/test/API/python_api/commandreturnobject/TestSBCommandReturnObject.py

Author: JDevlieghere

lldb/test/API/api/command-return-object/TestSBCommandReturnObject.py

@@ -24,3 +24,12 @@ def test_sb_command_return_object(self):
         # return exit code 0 to indicate success.  We can let this exception go
         # - the test harness will recognize it as a test failure.
         subprocess.check_call([self.driver_exe, self.driver_exe])
+
+    def test_get_command(self):
+        res = lldb.SBCommandReturnObject()
+        self.assertEqual(res.GetCommand(), "")
+
+        ci = self.dbg.GetCommandInterpreter()
+        ci.HandleCommand("help help", res)
+        self.assertTrue(res.Succeeded())
+        self.assertEqual(res.GetCommand(), "help help")