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/trie/src/lib.rs

@@ -19,6 +19,8 @@
 
 #![cfg_attr(not(feature = "std"), no_std)]
 
+extern crate alloc;
+
 #[cfg(feature = "std")]
 pub mod cache;
 mod error;
@@ -33,6 +35,8 @@ mod trie_stream;
 #[cfg(feature = "std")]
 pub mod proof_size_extension;
 
+use alloc::{borrow::Borrow, boxed::Box, vec, vec::Vec};
+use core::marker::PhantomData;
 /// Our `NodeCodec`-specific error.
 pub use error::Error;
 /// Various re-exports from the `hash-db` crate.
@@ -42,7 +46,6 @@ use hash_db::{Hasher, Prefix};
 pub use memory_db::{prefixed_key, HashKey, KeyFunction, PrefixedKey};
 /// The Substrate format implementation of `NodeCodec`.
 pub use node_codec::NodeCodec;
-use sp_std::{borrow::Borrow, boxed::Box, marker::PhantomData, vec::Vec};
 pub use storage_proof::{CompactProof, StorageProof};
 /// Trie codec reexport, mainly child trie support
 /// for trie compact proof.
@@ -500,7 +503,7 @@ pub struct KeySpacedDBMut<'a, DB: ?Sized, H>(&'a mut DB, &'a [u8], PhantomData<H
 /// Utility function used to merge some byte data (keyspace) and `prefix` data
 /// before calling key value database primitives.
 fn keyspace_as_prefix_alloc(ks: &[u8], prefix: Prefix) -> (Vec<u8>, Option<u8>) {
-	let mut result = sp_std::vec![0; ks.len() + prefix.0.len()];
+	let mut result = vec![0; ks.len() + prefix.0.len()];
 	result[..ks.len()].copy_from_slice(ks);
 	result[ks.len()..].copy_from_slice(prefix.0);
 	(result, prefix.1)