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/npos-elections/src/phragmms.rs

@@ -25,8 +25,8 @@ use crate::{
 	balance, setup_inputs, BalancingConfig, CandidatePtr, ElectionResult, ExtendedBalance,
 	IdentifierT, PerThing128, VoteWeight, Voter,
 };
+use alloc::{rc::Rc, vec, vec::Vec};
 use sp_arithmetic::{traits::Bounded, PerThing, Rational128};
-use sp_std::{prelude::*, rc::Rc};
 
 /// Execute the phragmms method.
 ///
@@ -232,8 +232,8 @@ pub(crate) fn apply_elected<AccountId: IdentifierT>(
 mod tests {
 	use super::*;
 	use crate::{Assignment, ElectionResult};
+	use alloc::rc::Rc;
 	use sp_runtime::{Perbill, Percent};
-	use sp_std::rc::Rc;
 
 	#[test]
 	fn basic_election_manual_works() {