Implement crypto byte array newtypes in term of a shared type (#3684)

Introduces `CryptoBytes` type defined as:

```rust
pub struct CryptoBytes<const N: usize, Tag = ()>(pub [u8; N], PhantomData<fn() -> Tag>);
```

The type implements a bunch of methods and traits which are typically
expected from a byte array newtype
(NOTE: some of the methods and trait implementations IMO are a bit
redundant, but I decided to maintain them all to not change too much
stuff in this PR)

It also introduces two (generic) typical consumers of `CryptoBytes`:
`PublicBytes` and `SignatureBytes`.

```rust
pub struct PublicTag;
pub PublicBytes<const N: usize, CryptoTag> = CryptoBytes<N, (PublicTag, CryptoTag)>;

pub struct SignatureTag;
pub SignatureBytes<const N: usize, CryptoTag> = CryptoBytes<N, (SignatureTag, CryptoTag)>;
```

Both of them use a tag to differentiate the two types at a higher level.
Downstream specializations will further specialize using a dedicated
crypto tag. For example in ECDSA:


```rust
pub struct EcdsaTag;

pub type Public = PublicBytes<PUBLIC_KEY_SERIALIZED_SIZE, EcdsaTag>;
pub type Signature = PublicBytes<PUBLIC_KEY_SERIALIZED_SIZE, EcdsaTag>;
```

Overall we have a cleaner and most importantly **consistent** code for
all the types involved

All these details are opaque to the end user which can use `Public` and
`Signature` for the cryptos as before

substrate/primitives/core/src/crypto.rs

@@ -39,7 +39,10 @@ pub use ss58_registry::{from_known_address_format, Ss58AddressFormat, Ss58Addres
 /// Trait to zeroize a memory buffer.
 pub use zeroize::Zeroize;
 
-pub use crate::address_uri::{AddressUri, Error as AddressUriError};
+pub use crate::{
+	address_uri::{AddressUri, Error as AddressUriError},
+	crypto_bytes::{CryptoBytes, PublicBytes, SignatureBytes},
+};
 
 /// The root phrase for our publicly known keys.
 pub const DEV_PHRASE: &str =