paymentsdb: fix SettleAttempt and FailAttempt to use caller-provided timestamps

The SQL backend introduced in this PR was ignoring the SettleTime and
FailTime fields provided in HTLCSettleInfo and HTLCFailInfo, instead
always recording time.Now() as the resolution timestamp. The KV backend
correctly serializes and deserializes these fields.

The timestamps are set by the caller using a mockable clock
(p.router.cfg.Clock.Now() in payment_lifecycle.go), so ignoring them
means the stored timestamp reflects when the DB write happened rather
than when the event occurred, breaking deterministic testing.

This commit also extends the test assertions in assertPaymentInfo to
verify that SettleTime and FailTime are correctly stored and retrieved
by the SQL backend, and updates the relevant call sites to pass explicit
timestamps so regressions are caught.

payments/db/sql_store.go

@@ -1629,7 +1629,7 @@ func (s *SQLStore) SettleAttempt(ctx context.Context, paymentHash lntypes.Hash,
 
 		err = db.SettleAttempt(ctx, sqlc.SettleAttemptParams{
 			AttemptIndex:   int64(attemptID),
-			ResolutionTime: time.Now(),
+			ResolutionTime: settleInfo.SettleTime.UTC(),
 			ResolutionType: int32(HTLCAttemptResolutionSettled),
 			SettlePreimage: settleInfo.Preimage[:],
 		})
@@ -1716,7 +1716,7 @@ func (s *SQLStore) FailAttempt(ctx context.Context, paymentHash lntypes.Hash,
 
 		err = db.FailAttempt(ctx, sqlc.FailAttemptParams{
 			AttemptIndex:   int64(attemptID),
-			ResolutionTime: time.Now(),
+			ResolutionTime: failInfo.FailTime.UTC(),
 			ResolutionType: int32(HTLCAttemptResolutionFailed),
 			FailureSourceIndex: sqldb.SQLInt32(
 				failInfo.FailureSourceIndex,