Add @RustDerive annotation and auto-generated Rust derives

Test: atest aidl_unittests
Change-Id: I11b3424f76e23a25bcd21dfe248fd590cbe6dac6
diff --git a/aidl_language.h b/aidl_language.h
index 7eae4c1..08bd8f3 100644
--- a/aidl_language.h
+++ b/aidl_language.h
@@ -169,6 +169,7 @@
     JAVA_ONLY_IMMUTABLE,
     FIXED_SIZE,
     DESCRIPTOR,
+    RUST_DERIVE,
   };
   static std::string TypeToString(Type type);
 
@@ -243,6 +244,7 @@
 
   const AidlAnnotation* UnsupportedAppUsage() const;
   const AidlAnnotation* JavaPassthrough() const;
+  const AidlAnnotation* RustDerive() const;
   const AidlTypeSpecifier* BackingType(const AidlTypenames& typenames) const;
   std::string ToString() const;