multi: upgrade new taproot TLVs to use tlv.OptionalRecordT

In this commit, we update new Taproot related TLVs (nonces, partial sig,
sig with nonce, etc). Along the way we were able to get rid of some
boiler plate, but most importantly, we're able to better protect against
API misuse (using a nonce that isn't initialized, etc) with the new
options API. In some areas this introduces a bit of extra boiler plate,
and where applicable I used some new helper functions to help cut down
on the noise.

Note to reviewers: this is done as a single commit, as changing the API
breaks all callers, so if we want things to compile it needs to be in a
wumbo commit.

lnwire/musig2.go

@@ -7,21 +7,33 @@ import (
 	"github.com/lightningnetwork/lnd/tlv"
 )
 
-const (
-	// NonceRecordType is the TLV type used to encode a local musig2 nonce.
-	NonceRecordType tlv.Type = 4
-)
+// NonceRecordTypeT is the TLV type used to encode a local musig2 nonce.
+type NonceRecordTypeT = tlv.TlvType4
 
-// Musig2Nonce represents a musig2 public nonce, which is the concatenation of
-// two EC points serialized in compressed format.
-type Musig2Nonce [musig2.PubNonceSize]byte
+// nonceRecordType is the TLV (integer) type used to encode a local musig2
+// nonce.
+var nonceRecordType tlv.Type = (NonceRecordTypeT)(nil).TypeVal()
+
+type (
+	// Musig2Nonce represents a musig2 public nonce, which is the
+	// concatenation of two EC points serialized in compressed format.
+	Musig2Nonce [musig2.PubNonceSize]byte
+
+	// Musig2NonceTLV is a TLV type that can be used to encode/decode a
+	// musig2 nonce. This is an optional TLV.
+	Musig2NonceTLV = tlv.RecordT[NonceRecordTypeT, Musig2Nonce]
+
+	// OptMusig2NonceTLV is a TLV type that can be used to encode/decode a
+	// musig2 nonce.
+	OptMusig2NonceTLV = tlv.OptionalRecordT[NonceRecordTypeT, Musig2Nonce]
+)
 
 // Record returns a TLV record that can be used to encode/decode the musig2
 // nonce from a given TLV stream.
 func (m *Musig2Nonce) Record() tlv.Record {
 	return tlv.MakeStaticRecord(
-		NonceRecordType, m, musig2.PubNonceSize, nonceTypeEncoder,
-		nonceTypeDecoder,
+		nonceRecordType, m, musig2.PubNonceSize,
+		nonceTypeEncoder, nonceTypeDecoder,
 	)
 }
 
@@ -48,3 +60,10 @@ func nonceTypeDecoder(r io.Reader, val interface{}, _ *[8]byte,
 		val, "lnwire.Musig2Nonce", l, musig2.PubNonceSize,
 	)
 }
+
+// SomeMusig2Nonce is a helper function that creates a musig2 nonce TLV.
+func SomeMusig2Nonce(nonce Musig2Nonce) OptMusig2NonceTLV {
+	return tlv.SomeRecordT(
+		tlv.NewRecordT[NonceRecordTypeT, Musig2Nonce](nonce),
+	)
+}