multi: use btcd's btcec/v2 and btcutil modules

This commit was previously split into the following parts to ease
review:
 - 2d746f68: replace imports
 - 4008f0fd: use ecdsa.Signature
 - 849e33d1: remove btcec.S256()
 - b8f6ebbd: use v2 library correctly
 - fa80bca9: bump go modules

tlv/go.mod

@@ -1,8 +1,10 @@
 module github.com/lightningnetwork/lnd/tlv
 
 require (
-	github.com/btcsuite/btcd v0.22.0-beta.0.20211005184431-e3449998be39
+	github.com/btcsuite/btcd v0.22.0-beta.0.20220207191057-4dc4ff7963b4
+	github.com/btcsuite/btcd/btcec/v2 v2.1.0
 	github.com/davecgh/go-spew v1.1.1
+	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.0.1
 )
 
 go 1.16