Fix CAMT Counterparty parsing

[abid76]

When both, creditor and debitor, are given in XML, creditor is chosen as counterparty, regardless if it's an incoming or outgoing transaction. As a result, the wrong counterparty is stored in the name and bank_code field after CAMT parsing of Commerzbank incoming transactions.

Summary

• Select the correct counterparty (name, IBAN, BIC) in CAMT parsing based on the credit/debit indicator: debtor for incoming (CRDT), creditor for outgoing (DBIT)
• Add unit tests with real-world CAMT fixtures from Fyrst Bank and Commerzbank (camt.052.001.08)

Test plan

• ./vendor/bin/phpunit Tests/Unit/CAMT/CAMTCounterpartyTest.php