Fix style issues in sweep_batcher_test.go

- Rename testPublishError to errTestPublish (ST1012)
- Add explicit type to all constants in const groups (SA9004)
- Fixes staticcheck style warnings

Author: hieblmi

sweepbatcher/sweep_batcher_test.go

@@ -638,15 +638,15 @@ type testTransactionPublisher struct {
 	attempts int
 }
 
-var testPublishError = errors.New("test publish error")
+var errTestPublish = errors.New("test publish error")
 
 // PublishTransaction publishes the transaction or fails it's the first attempt.
 func (p *testTransactionPublisher) PublishTransaction(ctx context.Context,
 	tx *wire.MsgTx, label string) error {
 
 	p.attempts++
 	if p.attempts == 1 {
-		return testPublishError
+		return errTestPublish
 	}
 
 	return p.WalletKitClient.PublishTransaction(ctx, tx, label)
@@ -4072,8 +4072,8 @@ func testSweepBatcherHandleSweepRace(t *testing.T, store testStore,
 	<-batcher.initDone
 
 	const (
-		sweepValue btcutil.Amount = 1_000_000
-		confHeight                = 605
+		sweepValue = btcutil.Amount(1_000_000)
+		confHeight = 605
 	)
 
 	sweepOutpoint := wire.OutPoint{
@@ -4534,8 +4534,8 @@ func TestSweepBatcherConfirmedBatchIncompleteSweeps(t *testing.T) {
 	swapStore := newLoopdbStore(t, sqlDB)
 
 	const (
-		sweepValue btcutil.Amount = 1_000_000
-		confHeight                = 777
+		sweepValue = btcutil.Amount(1_000_000)
+		confHeight = 777
 	)
 
 	ctx := context.Background()