feat(nix-compat/wire): add read_bytes[_unchecked]

This introduces a version reading sized byte packets. Both read_bytes,
accepting a range of allowed sizes, as well as read_bytes_unchecked,
which doesn't care, are added, including tests.

Co-Authored-By: picnoir <picnoir@alternativebit.fr>
Change-Id: I9fc1c61eb561105e649eecca832af28badfdaaa8
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11150
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: picnoir picnoir <picnoir@alternativebit.fr>
Tested-by: BuildkiteCI

tvix/nix-compat/src/wire/mod.rs

@@ -1,5 +1,8 @@
 //! Module parsing and emitting the wire format used by Nix, both in the
 //! nix-daemon protocol as well as in the NAR format.
 
+#[cfg(feature = "async")]
+pub mod bytes;
+
 #[cfg(feature = "async")]
 pub mod primitive;