tapgarden: switch to full locks and acquire them first in methods

Replace read-only locks with full mutex locks in MockKeyRing methods
for simplicity. Ensure the full lock is acquired as the first operation
in each method to maintain consistent and safe access.

Author: ffranr

tapgarden/mock.go

@@ -880,6 +880,7 @@ func NewMockKeyRing() *MockKeyRing {
 func (m *MockKeyRing) DeriveNextTaprootAssetKey(
 	ctx context.Context) (keychain.KeyDescriptor, error) {
 
+	// No need to lock mutex here, DeriveNextKey does that for us.
 	m.Called(ctx)
 
 	return m.DeriveNextKey(ctx, asset.TaprootAssetsKeyFamily)
@@ -888,6 +889,12 @@ func (m *MockKeyRing) DeriveNextTaprootAssetKey(
 func (m *MockKeyRing) DeriveNextKey(ctx context.Context,
 	keyFam keychain.KeyFamily) (keychain.KeyDescriptor, error) {
 
+	m.Lock()
+	defer func() {
+		m.KeyIndex++
+		m.Unlock()
+	}()
+
 	m.Called(ctx, keyFam)
 
 	select {
@@ -896,12 +903,6 @@ func (m *MockKeyRing) DeriveNextKey(ctx context.Context,
 	default:
 	}
 
-	m.Lock()
-	defer func() {
-		m.KeyIndex++
-		m.Unlock()
-	}()
-
 	priv, err := btcec.NewPrivateKey()
 	if err != nil {
 		return keychain.KeyDescriptor{}, err
@@ -925,10 +926,10 @@ func (m *MockKeyRing) DeriveNextKey(ctx context.Context,
 func (m *MockKeyRing) IsLocalKey(ctx context.Context,
 	d keychain.KeyDescriptor) bool {
 
-	m.Called(ctx, d)
+	m.Lock()
+	defer m.Unlock()
 
-	m.RLock()
-	defer m.RUnlock()
+	m.Called(ctx, d)
 
 	priv, ok := m.Keys[d.KeyLocator]
 	if ok && priv.PubKey().IsEqual(d.PubKey) {
@@ -945,8 +946,8 @@ func (m *MockKeyRing) IsLocalKey(ctx context.Context,
 }
 
 func (m *MockKeyRing) PubKeyAt(t *testing.T, idx uint32) *btcec.PublicKey {
-	m.RLock()
-	defer m.RUnlock()
+	m.Lock()
+	defer m.Unlock()
 
 	loc := keychain.KeyLocator{
 		Index:  idx,
@@ -962,8 +963,8 @@ func (m *MockKeyRing) PubKeyAt(t *testing.T, idx uint32) *btcec.PublicKey {
 }
 
 func (m *MockKeyRing) ScriptKeyAt(t *testing.T, idx uint32) asset.ScriptKey {
-	m.RLock()
-	defer m.RUnlock()
+	m.Lock()
+	defer m.Unlock()
 
 	loc := keychain.KeyLocator{
 		Index:  idx,
@@ -984,13 +985,13 @@ func (m *MockKeyRing) ScriptKeyAt(t *testing.T, idx uint32) asset.ScriptKey {
 func (m *MockKeyRing) DeriveSharedKey(_ context.Context, key *btcec.PublicKey,
 	locator *keychain.KeyLocator) ([sha256.Size]byte, error) {
 
+	m.Lock()
+	defer m.Unlock()
+
 	if locator == nil {
 		return [32]byte{}, fmt.Errorf("locator is nil")
 	}
 
-	m.RLock()
-	defer m.RUnlock()
-
 	priv, ok := m.Keys[*locator]
 	if !ok {
 		return [32]byte{}, fmt.Errorf("script key not found at index "+