multi: move Input interface and related code

This commit is a step to split the lnwallet package. It puts the Input
interface and implementations in a separate package along with all their
dependencies from lnwallet.

lnwallet/sigpool.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/btcsuite/btcd/btcec"
 	"github.com/btcsuite/btcd/wire"
+	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/lnwire"
 )
 
@@ -76,7 +77,7 @@ type SignJob struct {
 	// SignDesc is intended to be a full populated SignDescriptor which
 	// encodes the necessary material (keys, witness script, etc) required
 	// to generate a valid signature for the specified input.
-	SignDesc SignDescriptor
+	SignDesc input.SignDescriptor
 
 	// Tx is the transaction to be signed. This is required to generate the
 	// proper sighash for the input to be signed.
@@ -127,7 +128,7 @@ type SigPool struct {
 	started uint32 // To be used atomically.
 	stopped uint32 // To be used atomically.
 
-	signer Signer
+	signer input.Signer
 
 	verifyJobs chan VerifyJob
 	signJobs   chan SignJob
@@ -141,7 +142,7 @@ type SigPool struct {
 // NewSigPool creates a new signature pool with the specified number of
 // workers. The recommended parameter for the number of works is the number of
 // physical CPU cores available on the target machine.
-func NewSigPool(numWorkers int, signer Signer) *SigPool {
+func NewSigPool(numWorkers int, signer input.Signer) *SigPool {
 	return &SigPool{
 		signer:     signer,
 		numWorkers: numWorkers,