Only set bank account reference matching probability when contact is not found in other ways

Context
CiviBanking now contains an option to set probability of the matched contact when the contact is found based on the bank account.

At Velt bank accounts are stored at different contacts (e.g. members of houdsholds, or because someone has used his private bank account for local chapter businesses. Meaning that bank account is also stored at the local chapter in CiviCRM.

Original issue

Some payments where automatically matched against wrong contacts because of this mix up of bank accounts.
This issue is solved by lowering the bank account reference matching probability setting (we have set it at 0.9)

New issue

Contacts found based on their sepa mandate or based on a number in the purpose field. Are also set to 0.9 probability because of the matching on bank account. However in those case we are sure because the Sepa Mandate Reference is leading.

Solution

Only set the probability for found contacts based on the bank account when they are not already found in different ways.

I will soon post a pull request fixing this.

No file, test, or entry point is named in the issue. Trace the payment matching flow for SEPA mandates, purpose-field numbers, and bank-account matches, then verify that bank-account probability is changed only when no other matching method found the contact; add or update coverage for these cases.