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/provisioner/src/tests.rs

@@ -572,8 +572,9 @@ mod select_candidates {
 					_parent_hash,
 					PersistedValidationDataReq(_para_id, _assumption, tx),
 				)) => tx.send(Ok(Some(Default::default()))).unwrap(),
-				AllMessages::RuntimeApi(Request(_parent_hash, AvailabilityCores(tx))) =>
-					tx.send(Ok(mock_availability_cores.clone())).unwrap(),
+				AllMessages::RuntimeApi(Request(_parent_hash, AvailabilityCores(tx))) => {
+					tx.send(Ok(mock_availability_cores.clone())).unwrap()
+				},
 				AllMessages::CandidateBacking(CandidateBackingMessage::GetBackableCandidates(
 					hashes,
 					sender,