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

subxt/src/view_functions/mod.rs

@@ -0,0 +1,14 @@
+// Copyright 2019-2025 Parity Technologies (UK) Ltd.
+// This file is dual-licensed as Apache-2.0 or GPL-3.0.
+// see LICENSE for license details.
+
+//! Types associated with executing View Function calls.
+
+mod view_function_types;
+mod view_functions_client;
+
+pub use subxt_core::view_functions::payload::{
+    dynamic, DefaultPayload, DynamicPayload, Payload, StaticPayload,
+};
+pub use view_function_types::ViewFunctionsApi;
+pub use view_functions_client::ViewFunctionsClient;