lnworker: differentiate PaymentInfo by direction

Allows storing two different payment info of the same payment hash by
including the direction into the db key.
We create and store PaymentInfo for sending attempts and for requests (receiving),
if we try to pay ourself (e.g. through a channel rebalance) the checks
in `save_payment_info` would prevent this and throw an exception.
By storing the PaymentInfos of outgoing and incoming payments separately in
the db this collision is avoided and it makes it easier to reason about
which PaymentInfo belongs where.

tests/test_commands.py

@@ -11,6 +11,7 @@ import shutil
 import electrum
 from electrum.commands import Commands, eval_bool
 from electrum import storage, wallet
+from electrum.lnutil import RECEIVED
 from electrum.lnworker import RecvMPPResolution
 from electrum.wallet import Abstract_Wallet
 from electrum.address_synchronizer import TX_HEIGHT_UNCONFIRMED
@@ -509,7 +510,7 @@ class TestCommandsTestnet(ElectrumTestCase):
             )
         invoice = lndecode(invoice=result['invoice'])
         assert invoice.paymenthash.hex() == payment_hash
-        assert payment_hash in wallet.lnworker.payment_info
+        assert wallet.lnworker.get_payment_info(bytes.fromhex(payment_hash), direction=RECEIVED)
         assert payment_hash in wallet.lnworker.dont_expire_htlcs
         assert invoice.get_amount_sat() == 10000
         assert invoice.get_description() == "test"
@@ -520,7 +521,7 @@ class TestCommandsTestnet(ElectrumTestCase):
             payment_hash=payment_hash,
             wallet=wallet,
         )
-        assert payment_hash not in wallet.lnworker.payment_info
+        assert not wallet.lnworker.get_payment_info(bytes.fromhex(payment_hash), direction=RECEIVED)
         assert payment_hash not in wallet.lnworker.dont_expire_htlcs
         assert wallet.get_label_for_rhash(rhash=invoice.paymenthash.hex()) == ""
         assert cancel_result['cancelled'] == payment_hash