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/staking/src/offence.rs

@@ -18,10 +18,10 @@
 //! Common traits and types that are useful for describing offences for usage in environments
 //! that use staking.
 
+use alloc::vec::Vec;
 use codec::{Decode, Encode};
 use sp_core::Get;
 use sp_runtime::{transaction_validity::TransactionValidityError, DispatchError, Perbill};
-use sp_std::vec::Vec;
 
 use crate::SessionIndex;