sp-std removal from substrate/primitives (#3274)

This PR removes sp-std crate from substrate/primitives sub-directories.

For now crates that have `pub use` of sp-std or export macros that would
necessitate users of the macros to `extern crate alloc` have been
excluded from this PR.

There should be no breaking changes in this PR.

---------

Co-authored-by: Koute <koute@users.noreply.github.com>

substrate/primitives/block-builder/Cargo.toml

@@ -19,8 +19,7 @@ targets = ["x86_64-unknown-linux-gnu"]
 sp-api = { path = "../api", default-features = false }
 sp-inherents = { path = "../inherents", default-features = false }
 sp-runtime = { path = "../runtime", default-features = false }
-sp-std = { path = "../std", default-features = false }
 
 [features]
 default = ["std"]
-std = ["sp-api/std", "sp-inherents/std", "sp-runtime/std", "sp-std/std"]
+std = ["sp-api/std", "sp-inherents/std", "sp-runtime/std"]

substrate/primitives/block-builder/src/lib.rs

@@ -19,6 +19,8 @@
 
 #![cfg_attr(not(feature = "std"), no_std)]
 
+extern crate alloc;
+
 use sp_inherents::{CheckInherentsResult, InherentData};
 use sp_runtime::{traits::Block as BlockT, ApplyExtrinsicResult};
 
@@ -44,7 +46,7 @@ sp_api::decl_runtime_apis! {
 		/// Generate inherent extrinsics. The inherent data will vary from chain to chain.
 		fn inherent_extrinsics(
 			inherent: InherentData,
-		) -> sp_std::vec::Vec<<Block as BlockT>::Extrinsic>;
+		) -> alloc::vec::Vec<<Block as BlockT>::Extrinsic>;
 
 		/// Check that the inherents are valid. The inherent data will vary from chain to chain.
 		fn check_inherents(block: Block, data: InherentData) -> CheckInherentsResult;