python3Packages.setuptools-rust: add passthru test that uses maturinBuildHook

The test builds the PyO3 word_count example module using
setuptools-rust. The motivation is to have a trivial test that does
not regress for reasons unrelated to setuptools-rust or hook updates.

pkgs/development/python-modules/setuptools-rust/pyo3-test/default.nix

@@ -0,0 +1,21 @@
+{ callPackage
+, rustPlatform
+, setuptools-rust
+}:
+
+callPackage ../../../tools/rust/maturin/pyo3-test/generic.nix {
+  # Isolated builds break for this package, because PyO3 is not
+  # in the build root of the Python Package:
+  #
+  # https://github.com/pypa/pip/issues/6276
+  #
+  format = "setuptools";
+
+  nativeBuildInputs = [ setuptools-rust ] ++ (with rustPlatform; [
+    cargoSetupHook
+    rust.cargo
+    rust.rustc
+  ]);
+
+  sourceRoot = "source/examples/word-count";
+}