CLC-4247: finishing QA CFV tests for My Finances

This includes two new specs, plus supporting code:
* my_finances_ui_details_page_spec - uses Oski's account to verify sorting and filtering for transaction lists
* my_finances_data_transaction_detail_spec - iterates through accounts to verify the permutations of detail shown in different transaction scenarios
An existing test is also updated:
* my_finances_data_account_summary_spec - an additional check that open transactions and account balance are in sync.