Allow usage of path in construct_runtime! (#8801)

* Allow usage of path in construct_runtime!

* Fix whitespace

* Fix whitespace

* Make expand_runtime_metadata accept slice instead of Iterator

* Include Call and Event in construct_runtime for testing

* Migrate impl_outer_event to proc macro

* Fix integrity_test_works

* Update UI test expectations

* Factor in module path while generating enum variant or fn names

* Use ParseStream::lookahead for more helpful error messages

* Remove generating outer_event_metadata

* Ensure pallets with different paths but same last path segment can coexist

* Remove unnecessary generated function

* Migrate decl_outer_config to proc macro

* Add default_filter test for expand_outer_origin

* Allow crate, self and super keywords to appear in pallet path

* Add UI test for specifying empty pallet paths in construct_runtime

substrate/frame/support/test/tests/construct_runtime_ui/empty_pallet_path.rs

@@ -0,0 +1,13 @@
+use frame_support::construct_runtime;
+
+construct_runtime! {
+	pub enum Runtime where
+		Block = Block,
+		NodeBlock = Block,
+		UncheckedExtrinsic = UncheckedExtrinsic
+	{
+		system: ,
+	}
+}
+
+fn main() {}

substrate/frame/support/test/tests/construct_runtime_ui/empty_pallet_path.stderr

@@ -0,0 +1,5 @@
+error: expected one of: `crate`, `self`, `super`, identifier
+ --> $DIR/empty_pallet_path.rs:9:11
+  |
+9 |         system: ,
+  |                 ^

substrate/frame/support/test/tests/construct_runtime_ui/invalid_module_details.stderr

@@ -1,4 +1,4 @@
-error: expected curly braces
+error: expected one of: identifier, curly braces, `<`
  --> $DIR/invalid_module_details.rs:9:19
   |
 9 |         system: System::(),