keyring: remove lazy_static public keys hash maps (#2387)

The `lazy_static` package does not work well in `no-std`: it requires
`spin_no_std` feature, which also will propagate into `std` if enabled.
This is not what we want.

This PR removes public/private key hash-maps and replaces them with
simple static byte arrays.

`&T` versions of `AsRef/Deref/From` traits implementation were removed.

Little const helper for converting hex strings into array during compile
time was also added. (somewhat similar to _hex_literal_).

---------

Co-authored-by: command-bot <>
Co-authored-by: Koute <koute@users.noreply.github.com>

substrate/primitives/core/src/lib.rs

@@ -51,6 +51,7 @@ pub mod hashing;
 
 #[cfg(feature = "full_crypto")]
 pub use hashing::{blake2_128, blake2_256, keccak_256, twox_128, twox_256, twox_64};
+pub mod const_hex2array;
 pub mod crypto;
 pub mod hexdisplay;
 pub use paste;