Move Externalities into its own crate (#3775)

* Move `Externalities` into `substrate-externalities`

- `Externalities` now support generic extensions
- Split of `primtives-storage` for storage primitive types

* Move the externalities scoping into `substrate-externalities`

* Fix compilation

* Review feedback

* Adds macro for declaring extensions

* Fix benchmarks

* Introduce `ExtensionStore` trait

* Last review comments

* Implement it for `ExtensionStore`

substrate/core/sr-primitives/Cargo.toml

@@ -16,6 +16,7 @@ runtime_io = { package = "sr-io", path = "../sr-io", default-features = false }
 log = { version = "0.4.8", optional = true }
 paste = "0.1.6"
 rand = { version = "0.7.2", optional = true }
+externalities = { package = "substrate-externalities", path = "../externalities", optional = true }
 impl-trait-for-tuples = "0.1.2"
 
 [dev-dependencies]
@@ -36,4 +37,5 @@ std = [
 	"primitives/std",
 	"app-crypto/std",
 	"rand",
+	"externalities",
 ]

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

@@ -67,6 +67,9 @@ pub use sr_arithmetic::{
 /// Re-export 128 bit helpers from sr_arithmetic
 pub use sr_arithmetic::helpers_128bit;
 
+#[cfg(feature = "std")]
+pub use externalities::set_and_run_with_externalities;
+
 /// An abstraction over justification for a block's validity under a consensus algorithm.
 ///
 /// Essentially a finality proof. The exact formulation will vary between consensus

substrate/core/sr-primitives/src/offchain/http.rs

@@ -512,16 +512,18 @@ impl<'a> HeadersIterator<'a> {
 #[cfg(test)]
 mod tests {
 	use super::*;
-	use runtime_io::{TestExternalities, with_externalities};
+	use crate::set_and_run_with_externalities;
+	use runtime_io::TestExternalities;
 	use substrate_offchain::testing;
+	use primitives::offchain::OffchainExt;
 
 	#[test]
 	fn should_send_a_basic_request_and_get_response() {
 		let (offchain, state) = testing::TestOffchainExt::new();
 		let mut t = TestExternalities::default();
-		t.set_offchain_externalities(offchain);
+		t.register_extension(OffchainExt::new(offchain));
 
-		with_externalities(&mut t, || {
+		set_and_run_with_externalities(&mut t, || {
 			let request: Request = Request::get("http://localhost:1234");
 			let pending = request
 				.add_header("X-Auth", "hunter2")
@@ -560,9 +562,9 @@ mod tests {
 	fn should_send_a_post_request() {
 		let (offchain, state) = testing::TestOffchainExt::new();
 		let mut t = TestExternalities::default();
-		t.set_offchain_externalities(offchain);
+		t.register_extension(OffchainExt::new(offchain));
 
-		with_externalities(&mut t, || {
+		set_and_run_with_externalities(&mut t, || {
 			let pending = Request::default()
 				.method(Method::Post)
 				.url("http://localhost:1234")