Embed runtime version as a custom section (#8688)

* emit a custom section from impl_runtime_apis!

This change emits a custom section from the impl_runtime_apis! proc macro.

Each implemented API will result to emitting a link section `runtime_apis`.
During linking all sections with this name will be concatenated and
placed into the final wasm binary under the same name.

* Introduce `runtime_version` proc macro

This macro takes an existing `RuntimeVersion` const declaration, parses
it and emits the version information in form of a linking section.
Ultimately such a linking section will result into a custom wasm
section.

* Parse custom wasm section for runtime version

* Apply suggestions from code review

Co-authored-by: David <dvdplm@gmail.com>

* Fix sc-executor integration tests

* Nits

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Refactor apis section deserialization

* Fix version decoding

* Reuse uncompressed value for CallInWasm

* Log on decompression error

* Simplify if

* Reexport proc-macro from sp_version

* Merge ReadRuntimeVersionExt

* Export `read_embedded_version`

* Fix test

* Simplify searching for custom section

Co-authored-by: David <dvdplm@gmail.com>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/client/executor/common/src/runtime_blob/runtime_blob.rs

@@ -27,6 +27,17 @@ pub struct RuntimeBlob {
 }
 
 impl RuntimeBlob {
+	/// Create `RuntimeBlob` from the given wasm code. Will attempt to decompress the code before
+	/// deserializing it.
+	///
+	/// See [`sp_maybe_compressed_blob`] for details about decompression.
+	pub fn uncompress_if_needed(wasm_code: &[u8]) -> Result<Self, WasmError> {
+		use sp_maybe_compressed_blob::CODE_BLOB_BOMB_LIMIT;
+		let wasm_code = sp_maybe_compressed_blob::decompress(wasm_code, CODE_BLOB_BOMB_LIMIT)
+			.map_err(|e| WasmError::Other(format!("Decompression error: {:?}", e)))?;
+		Self::new(&wasm_code)
+	}
+
 	/// Create `RuntimeBlob` from the given wasm code.
 	///
 	/// Returns `Err` if the wasm code cannot be deserialized.
@@ -85,9 +96,23 @@ impl RuntimeBlob {
 		})
 	}
 
+	/// Scans the wasm blob for the first section with the name that matches the given. Returns the
+	/// contents of the custom section if found or `None` otherwise.
+	pub fn custom_section_contents(&self, section_name: &str) -> Option<&[u8]> {
+		self.raw_module
+			.custom_sections()
+			.find(|cs| cs.name() == section_name)
+			.map(|cs| cs.payload())
+		}
+
 	/// Consumes this runtime blob and serializes it.
 	pub fn serialize(self) -> Vec<u8> {
 		serialize(self.raw_module)
 			.expect("serializing into a vec should succeed; qed")
 	}
+
+	/// Destructure this structure into the underlying parity-wasm Module.
+	pub fn into_inner(self) -> RawModule {
+		self.raw_module
+	}
 }