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/consensus/grandpa/src/lib.rs

@@ -19,9 +19,12 @@
 
 #![cfg_attr(not(feature = "std"), no_std)]
 
+extern crate alloc;
+
 #[cfg(feature = "serde")]
 use serde::Serialize;
 
+use alloc::vec::Vec;
 use codec::{Codec, Decode, Encode};
 use scale_info::TypeInfo;
 #[cfg(feature = "std")]
@@ -30,7 +33,6 @@ use sp_runtime::{
 	traits::{Header as HeaderT, NumberFor},
 	ConsensusEngineId, RuntimeDebug,
 };
-use sp_std::vec::Vec;
 
 /// The log target to be used by client code.
 pub const CLIENT_LOG_TARGET: &str = "grandpa";