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/core/approval-voting/src/backend.rs

@@ -132,10 +132,10 @@ impl<'a, B: 'a + Backend> OverlayedBackend<'a, B> {
 	}
 
 	pub fn is_empty(&self) -> bool {
-		self.block_entries.is_empty() &&
-			self.candidate_entries.is_empty() &&
-			self.blocks_at_height.is_empty() &&
-			self.stored_block_range == BlockRangeStatus::NotModified
+		self.block_entries.is_empty()
+			&& self.candidate_entries.is_empty()
+			&& self.blocks_at_height.is_empty()
+			&& self.stored_block_range == BlockRangeStatus::NotModified
 	}
 
 	pub fn load_all_blocks(&self) -> SubsystemResult<Vec<Hash>> {