Add Java reflection bindings to the distribution (#7851)

The distributions for C++ and Python include the generated reflection
bindings but are currently missing from the other language packages.
This will bring the Java package generated for releases closer to
feature parity with the C++ and Python release artifacts.

scripts/generate_code.py

@@ -507,6 +507,12 @@ if not args.skip_gen_reflection:
 # Python Reflection
 flatc_reflection(["-p"], "python/flatbuffers", "reflection")
 
+# Java Reflection
+flatc_reflection(
+    ["-j", "--java-package-prefix", "com.google.flatbuffers"],
+    "java/src/main/java", "com/google/flatbuffers/reflection"
+)
+
 # Annotation