Move GetBestBlockResult to btcws.
Move GetBestBlockResult to btcws.

jrick/dcrwallet,Stash-Crypto/btcwallet,jrick/btcwallet,btcsuite/btcwallet,jrick/dcrwallet,Roasbeef/btcwallet,jrick/btcwallet,synrg-labs/btcwallet,btcsuite/btcwallet,synrg-labs/btcwallet,decred/dcrwallet,Roasbeef/btcwallet,Stash-Crypto/btcwallet,decred/dcrwallet