feat(tvix/nix-compat-derive): Add deriver for NixDeserialize

This adds a nix-compat-derive derive crate that implements a deriver
for NixDeserialize implementations. This is to reduce the amount of
code needed to implement deserialization for all the types used by
the Nix daemon protocol.

Change-Id: I484724b550e8a1d5e9adad9555d9dc1374ae95c2
Reviewed-on: https://cl.tvl.fyi/c/depot/+/12022
Autosubmit: Brian Olsen <me@griff.name>
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>

tvix/nix-compat-derive-tests/tests/ui/deserialize_missing_default_path.rs

@@ -0,0 +1,12 @@
+use nix_compat_derive::NixDeserialize;
+
+#[derive(NixDeserialize)]
+pub struct Value(String);
+
+#[derive(NixDeserialize)]
+pub struct Test {
+    #[nix(version = "20..", default = "Value::make_default")]
+    version: Value,
+}
+
+fn main() {}