Auto guess inner class's this$0 field names

[liach]

Currently, proguard obfuscates inner class's reference field to the outer class for instance inner classes. As a result, these fields have intermediary names assigned, but these names are very hard to find out and to be used by modders. (They need to javap the inner class to find out the correct intermediary name) It would be a grace if we can automatically map these outer class reference fields' names to this$0 instead, which would allow easier shadowing usage by modders writing mixins