Rewrite impl_runtime_apis! and decl_runtime_apis! as proc-macro (#1174)

* Rewrites `impl_runtime_apis!` macro as `proc-macro`

* Adds some documentation

* Require the `impl_runtime_apis` to use a path for accessing the trait

* Make the runtime implement `GetNodeBlockType`

* Moves first chunk of runtime api code into the `impl_runtime_apis` macro

This also renames `ClientWithApi` into `RuntimeApi`.

* Make `impl_runtime_apis` use `runtime` api version automatically

* `decl_runtime_apis` automatically adds `Block: BlockT` as generic parameter

* Remove function generic arguments in block builder api

* Remove some unnused stuff from the `decl_runtime_apis` macro

* Make `InherentData` working again

* Make `impl_runtime_apis!` implement the `RuntimeApi` side as well

* Make it compile again after rebasing with master

* Split `sr-api-macros` into multiple files

* Reimplement `decl_runtime_apis!` as proc_macro

* Use `decl_runtime_apis!` for `Core` as well and improve error reporting

* Adds documentation for `decl_runtime_apis!` and `impl_runtime_apis!`

* Move some code

* Adds compile fail tests

* Adds a test and fixes some bugs

* Make `impl_runtime_apis!` support `_` as parameter name

* Fixes build errors with wasm

* Wasm rebuild after master rebase

* Apply suggestions from code review

Co-Authored-By: bkchr <bkchr@users.noreply.github.com>

* Addresses some grumbles

* Adds test to ensure that method signatures need to match

* New wasm files

substrate/core/sr-primitives/src/lib.rs

@@ -462,6 +462,35 @@ macro_rules! impl_outer_log {
 	};
 }
 
+//TODO: https://github.com/paritytech/substrate/issues/1022
+/// Inherent data to include in a block.
+#[derive(Encode, Decode)]
+pub struct InherentData {
+	/// Current timestamp.
+	pub timestamp: u64,
+	/// Indices of offline validators.
+	pub consensus: Vec<u32>,
+}
+
+impl InherentData {
+	/// Create a new `InherentData` instance.
+	pub fn new(timestamp: u64, consensus: Vec<u32>) -> Self {
+		Self {
+			timestamp,
+			consensus,
+		}
+	}
+}
+
+//TODO: https://github.com/paritytech/substrate/issues/1022
+/// Error type used while checking inherents.
+#[derive(Encode)]
+#[cfg_attr(feature = "std", derive(Decode))]
+pub enum CheckInherentError {
+	TimestampInFuture(u64),
+	Other(RuntimeString),
+}
+
 #[cfg(test)]
 mod tests {
 	use substrate_primitives::hash::H256;