feat(tvix/nix-compat/nix_daemon/version): add ProtocolVersion

This provides a nice wrapper struct to deal with versions.

Change-Id: I6acc03bc9f8d84a0583196073b52776c45d3fe92
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11454
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Reviewed-by: picnoir picnoir <picnoir@alternativebit.fr>

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

@@ -1 +1,4 @@
 pub mod worker_protocol;
+
+mod protocol_version;
+pub use protocol_version::ProtocolVersion;