rename Query::map() to try_map() and nail down some semantics

sqlx-core/src/executor.rs

@@ -81,22 +81,6 @@ where
     }
 }
 
-#[allow(unused_macros)]
-macro_rules! impl_execute_for_query {
-    ($db:ty) => {
-        impl<'q> $crate::executor::Execute<'q, $db> for $crate::query::Query<'q, $db> {
-            fn into_parts(
-                self,
-            ) -> (
-                &'q str,
-                Option<<$db as $crate::database::Database>::Arguments>,
-            ) {
-                (self.query, Some(self.arguments))
-            }
-        }
-    };
-}
-
 impl<T> Executor for &'_ mut T
 where
     T: Executor,