* Clean Any interface
+ removed Any.Pack method. This method is not needed, because we have specialized
functions for createing new Any values. It could be used inappropriately with existing
Any objects.
* removed deprecated PackAny function
* fix linter issue
* update nil handling
* NewAnyWithValue returns error on nil instead of panic
* NewMsgCreateValidator: handle nil pubkey
* Remove AsAny and tx builder workarounds
* fix linter issue
* Add AsAny methods to TxBuilder and StdTxConfig, but keep intoAny interface private
* remove tx.PubKeyToAny
* cosmetic updates
* fix method interface
* move ProtoTxProvider to x/auth/tx