Standardize unimplemented API failures

tests/compat/tests/shim_failure.rs

@@ -0,0 +1,28 @@
+use libremetaverse_types::NotImplemented;
+
+const MEMBER: &str = "M:LibreMetaverse.GridClient.Login(System.String)";
+
+#[test]
+fn every_api_crate_exposes_the_shared_error() {
+    macro_rules! assert_aliases {
+        ($($error:path),+ $(,)?) => {$({
+            let _: $error = NotImplemented::new(MEMBER);
+        })+};
+    }
+
+    assert_aliases!(
+        libremetaverse::Error,
+        libremetaverse_imaging::Error,
+        libremetaverse_imaging_skia::Error,
+        libremetaverse_lsl_tools::Error,
+        libremetaverse_prim_mesher::Error,
+        libremetaverse_rendering_mesh_foundry::Error,
+        libremetaverse_rendering_simple::Error,
+        libremetaverse_rlv::Error,
+        libremetaverse_structured_data::Error,
+        libremetaverse_types::Error,
+        libremetaverse_utilities::Error,
+        libremetaverse_voice_vivox::Error,
+        libremetaverse_voice_webrtc::Error,
+    );
+}