style: Migrate to stable-only rustfmt configuration

- Remove nightly-only features from .rustfmt.toml and vendor/ss58-registry/rustfmt.toml
- Removed features: imports_granularity, wrap_comments, comment_width,
  reorder_impl_items, spaces_around_ranges, binop_separator,
  match_arm_blocks, trailing_semicolon, trailing_comma
- Format all 898 affected files with stable rustfmt
- Ensures long-term reliability without nightly toolchain dependency

pezkuwi/node/subsystem-test-helpers/src/lib.rs

@@ -80,10 +80,11 @@ impl<T> Sink<T> for SingleItemSink<T> {
 		let mut state = self.0.lock();
 
 		match *state {
-			SinkState::Empty { ref mut read_waker } =>
+			SinkState::Empty { ref mut read_waker } => {
 				if let Some(waker) = read_waker.take() {
 					waker.wake();
-				},
+				}
+			},
 			_ => panic!("start_send called outside of empty sink state ensured by poll_ready"),
 		}