config: add litecoin testnet4 parameters to the set of RPC parameters
config: add litecoin testnet4 parameters to the set of RPC parameters

This commit adds the new litecoin testnet4 parameters to the set of
currently supported RPC parameters. Due to the way golfing handles
namespacing we had to implement a bit of a hack in order to allow both
litecoin and bitcoin parameters to be used within the codebase. In the
future, we may create a structure similar to chaincfg.Params _directly_
within lnd so the implementation can be a bit cleaner.

LightningNetwork/lnd,AndrewSamokhvalov/lnd,aakselrod/lnd,ddustin/lnd,aakselrod/lnd,LightningNetwork/lnd,AndrewSamokhvalov/lnd,ddustin/lnd