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

bizinikiwi/client/merkle-mountain-range/src/aux_schema.rs

@@ -65,8 +65,12 @@ where
 	match version {
 		None => (),
 		Some(1) => return load_decode::<_, PersistedState<B>>(backend, GADGET_STATE),
-		other =>
-			return Err(ClientError::Backend(format!("Unsupported MMR aux DB version: {:?}", other))),
+		other => {
+			return Err(ClientError::Backend(format!(
+				"Unsupported MMR aux DB version: {:?}",
+				other
+			)))
+		},
 	}
 
 	// No persistent state found in DB.

bizinikiwi/client/merkle-mountain-range/src/test_utils.rs

@@ -94,8 +94,9 @@ impl MmrBlock {
 				node,
 				self.parent_hash(),
 			),
-			OffchainKeyType::Canon =>
-				NodesUtils::node_canon_offchain_key(MockRuntimeApi::INDEXING_PREFIX, node),
+			OffchainKeyType::Canon => {
+				NodesUtils::node_canon_offchain_key(MockRuntimeApi::INDEXING_PREFIX, node)
+			},
 		}
 	}
 }