Gracefully handle duplicated module names in 'extra-module-info' bridge

[jjohannes]

To no longer fail with and IllegalStateException: Duplicate key exception in cases where the other plugin is configured like this:

// Two variations of the same module (with the same Module Name)
extraJavaModuleInfo {
    module("com.google.protobuf:protobuf-javalite", "com.google.protobuf")
    module("com.google.protobuf:protobuf-java", "com.google.protobuf")
}