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/node/runtime/wasm/Cargo.lock

@@ -829,7 +829,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "proc-macro2 0.4.19 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 0.15.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.15.22 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -896,6 +896,15 @@ dependencies = [
  "unreachable 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "sr-api-macros"
+version = "0.1.0"
+dependencies = [
+ "proc-macro2 0.4.19 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.15.22 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "sr-io"
 version = "0.1.0"
@@ -1240,6 +1249,7 @@ dependencies = [
  "parity-codec 2.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "slog 2.4.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sr-api-macros 0.1.0",
  "sr-primitives 0.1.0",
  "sr-std 0.1.0",
  "sr-version 0.1.0",
@@ -1394,7 +1404,7 @@ dependencies = [
 
 [[package]]
 name = "syn"
-version = "0.15.6"
+version = "0.15.22"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "proc-macro2 0.4.19 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1851,7 +1861,7 @@ dependencies = [
 "checksum stable_deref_trait 1.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "dba1a27d3efae4351c8051072d619e3ade2820635c3958d826bfea39d59b54c8"
 "checksum static_assertions 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)" = "c19be23126415861cb3a23e501d34a708f7f9b2183c5252d690941c2e69199d5"
 "checksum syn 0.14.9 (registry+https://github.com/rust-lang/crates.io-index)" = "261ae9ecaa397c42b960649561949d69311f08eeaea86a65696e6e46517cf741"
-"checksum syn 0.15.6 (registry+https://github.com/rust-lang/crates.io-index)" = "854b08a640fc8f54728fb95321e3ec485b365a97fe47609797c671addd1dde69"
+"checksum syn 0.15.22 (registry+https://github.com/rust-lang/crates.io-index)" = "ae8b29eb5210bc5cf63ed6149cbf9adfc82ac0be023d8735c176ee74a2db4da7"
 "checksum take_mut 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "f764005d11ee5f36500a149ace24e00e3da98b0158b3e2d53a7495660d3f4d60"
 "checksum thread_local 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)" = "c6b53e329000edc2b34dbe8545fd20e55a333362d0a321909685a19bd28c3f1b"
 "checksum time 0.1.40 (registry+https://github.com/rust-lang/crates.io-index)" = "d825be0eb33fda1a7e68012d51e9c7f451dc1a69391e7fdc197060bb8c56667b"