zcash_encoding: Remove dependency on byteorder crate

[str4d]

librustzcash/components/zcash_encoding/src/lib.rs

Line 11 in dec3024

use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt};

We currently rely on the ReadBytesExt and WriteBytesExt traits, which are built around std::io and thus require the std feature flag of byteorder. This makes the zcash_encoding crate incompatible with no-std environments (even if they support alloc).

We should move away from the byteorder crate in favour of the parsing methods on native types (like u64::from_le_bytes), which have been in Rust since 1.32 (well below our MSRV for zcash_encoding of 1.56.1).