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/statement-store/src/lib.rs

@@ -20,13 +20,15 @@
 
 //! A crate which contains statement-store primitives.
 
+extern crate alloc;
+
+use alloc::vec::Vec;
 use codec::{Decode, Encode};
 use scale_info::TypeInfo;
 use sp_application_crypto::RuntimeAppPublic;
 #[cfg(feature = "std")]
 use sp_core::Pair;
 use sp_runtime_interface::pass_by::PassByCodec;
-use sp_std::vec::Vec;
 
 /// Statement topic.
 pub type Topic = [u8; 32];