Metadata V16: Implement support for Pallet View Functions (#1981)

* Support Pallet View Functions in Subxt

* fmt

* clippy

* Move a little view function logic to subxt_core

* clippy

* Add back check that prob isnt needed

* avoid vec macro in core

* Add view funciton test and apply various fixes to get it working

* Add test for dynamic view fn call and fix issues

* clippy

* fix test-runtime

* fmt

* remove export

* avoid vec for nostd core

* use const instead of fn for view fn call name

* Update to support latest unstable metadata

* Update metadata stripping tests for new v16 version

testing/test-runtime/src/lib.rs

@@ -7,7 +7,7 @@
 /// The SCALE encoded metadata obtained from a local run of a substrate node.
 pub static METADATA: &[u8] = include_bytes!(concat!(
     env!("OUT_DIR"),
-    "/test_node_runtime_metadata.scale"
+    "/test_node_runtime_metadata_v15.scale"
 ));
 
 include!(concat!(env!("OUT_DIR"), "/runtime.rs"));