fix: Wrong bank_ac_no filter + simplify logic in automatch

[marination]

Closes alyf-de/banking#135

Issue

File "apps/erpnext/erpnext/accounts/doctype/bank_transaction/auto_match_party.py", line 58, in match_account_in_party
    party_result = frappe.db.get_all(
  File "apps/frappe/frappe/database/database.py", line 810, in get_all
    return frappe.get_all(*args, **kwargs)
  File "apps/frappe/frappe/__init__.py", line 1938, in get_all
    return get_list(doctype, *args, **kwargs)
  File "apps/frappe/frappe/__init__.py", line 1910, in get_list
    return frappe.model.db_query.DatabaseQuery(doctype).execute(*args, **kwargs)
  File "apps/frappe/frappe/model/db_query.py", line 190, in execute
    result = self.build_and_run()
  File "apps/frappe/frappe/model/db_query.py", line 231, in build_and_run
    return frappe.db.sql(
  File "apps/frappe/frappe/database/database.py", line 244, in sql
    self._cursor.execute(query, values)
  File "env/lib/python3.10/site-packages/pymysql/cursors.py", line 153, in execute
    result = self._query(query)
  File "env/lib/python3.10/site-packages/pymysql/cursors.py", line 322, in _query
    conn.query(q)
  File "env/lib/python3.10/site-packages/pymysql/connections.py", line 563, in query
    self._affected_rows = self._read_query_result(unbuffered=unbuffered)
  File "env/lib/python3.10/site-packages/pymysql/connections.py", line 825, in _read_query_result
    result.read()
  File "env/lib/python3.10/site-packages/pymysql/connections.py", line 1199, in read
    first_packet = self.connection._read_packet()
  File "env/lib/python3.10/site-packages/pymysql/connections.py", line 775, in _read_packet
    packet.raise_for_error()
  File "env/lib/python3.10/site-packages/pymysql/protocol.py", line 219, in raise_for_error
    err.raise_mysql_exception(self._data)
  File "env/lib/python3.10/site-packages/pymysql/err.py", line 150, in raise_mysql_exception
    raise errorclass(errno, errval)
pymysql.err.OperationalError: (1054, "Unknown column 'tabBank Account.bank_ac_no' in 'where clause'")

• or_filters["bank_ac_no"] gets set for "Employee" and then when the loop moves on to the next party type, this value persists, since or_filters is instantiated outside the loop and does not get refreshed
• The loop is unnecessary as Supplier and Customer do not have any data to extract and match here

Fix

• Simplify the logic (Look in Bank Account first and then Employee) and remove the loop (we were checking in "Bank Account" in every loop which was plain ... futile)
• Return fast if filter data is unavailable
• Misc: Sourcery refactors

Already has tests that should check correctness

To Test

• Create a Bank account and an IBAN to it "DE123456789" and set a party and party type in it
• In Accounts Settings > Banking > enable automatic party matching
• Create a Bank Transaction and set the Party IBAN as "DE123456789"
• Submit the transaction > The Party must be set
• The same thing can be achieved by setting the IBAN in the "Employee" doctype (remove party from bank account)