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/phragmen.rs

@@ -24,12 +24,12 @@ use crate::{
 	balancing, setup_inputs, BalancingConfig, CandidatePtr, ElectionResult, ExtendedBalance,
 	IdentifierT, PerThing128, VoteWeight, Voter,
 };
+use alloc::vec::Vec;
 use sp_arithmetic::{
 	helpers_128bit::multiply_by_rational_with_rounding,
 	traits::{Bounded, Zero},
 	Rational128, Rounding,
 };
-use sp_std::prelude::*;
 
 /// The denominator used for loads. Since votes are collected as u64, the smallest ratio that we
 /// might collect is `1/approval_stake` where approval stake is the sum of votes. Hence, some number