refactor(tvix/nix-compat): move worker_protocol into nix_daemon mod

This doesn't have much to do with the plain "wire" format, it's merely
one user of it.

Also, use the more "public" `wire::` API to read/write bytes, strings,
bools and u64s.

Change-Id: I98dddcc3004dfde7a0c009958fe84a840f77b188
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11390
Tested-by: BuildkiteCI
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Reviewed-by: Brian Olsen <me@griff.name>

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

@@ -0,0 +1 @@
+pub mod worker_protocol;