move fetch metadata to a separate crate subxt_utils_fetchmetadata (#1829)

* macros: feature-gate jsonrpsee/fetch metadata url

* make CI happy

* Update codegen/src/error.rs

* extract `fetch-metdata` to separate crate

* add missing license headers

* introduce subxt-utils crate

* add missing files

* codegen: remove unused hex crate

* fix test build

* move subxt_utils -> subxt_utils_fetchmetadata

* cargo fmt

* runtime-path -> runtime-metadata-path

* Update utils/fetch-metadata/src/lib.rs

utils/fetch-metadata/src/macros.rs

@@ -0,0 +1,22 @@
+// Copyright 2019-2024 Parity Technologies (UK) Ltd.
+// This file is dual-licensed as Apache-2.0 or GPL-3.0.
+// see LICENSE for license details.
+
+macro_rules! cfg_feature {
+	($feature:literal, $($item:item)*) => {
+		$(
+			#[cfg(feature = $feature)]
+			#[cfg_attr(docsrs, doc(cfg(feature = $feature)))]
+			$item
+		)*
+	}
+}
+
+macro_rules! cfg_fetch_from_url {
+	($($item:item)*) => {
+		crate::macros::cfg_feature!("url", $($item)*);
+	};
+}
+
+#[allow(unused)]
+pub(crate) use {cfg_feature, cfg_fetch_from_url};