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/state-machine/src/lib.rs

@@ -20,6 +20,8 @@
 #![warn(missing_docs)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
+extern crate alloc;
+
 pub mod backend;
 #[cfg(feature = "std")]
 mod basic;
@@ -118,8 +120,8 @@ pub type DefaultError = String;
 pub struct DefaultError;
 
 #[cfg(not(feature = "std"))]
-impl sp_std::fmt::Display for DefaultError {
-	fn fmt(&self, f: &mut sp_std::fmt::Formatter) -> sp_std::fmt::Result {
+impl core::fmt::Display for DefaultError {
+	fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
 		write!(f, "DefaultError")
 	}
 }