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/sassafras/src/vrf.rs

@@ -18,9 +18,10 @@
 //! Utilities related to VRF input, pre-output and signatures.
 
 use crate::{Randomness, TicketBody, TicketId};
+#[cfg(not(feature = "std"))]
+use alloc::vec::Vec;
 use scale_codec::Encode;
 use sp_consensus_slots::Slot;
-use sp_std::vec::Vec;
 
 pub use sp_core::bandersnatch::{
 	ring_vrf::{RingProver, RingVerifier, RingVerifierData, RingVrfSignature},