In "Contribution Aggregate" custom search, fix "contribution type" filter to work with CiviAccounts schema changes

Issue CRM-10807 introduced a "contribution type" filter in the Contribution Aggregate custom search. However, after -r43570, this creates an error when opening the Contribution Aggregate custom search:
"Fatal error: Call to undefined method CRM_Contribute_PseudoConstant::contributionType() in /[path]/civicrm/CRM/Contact/Form/Search/Custom/ContributionAggregate.php on line 77" This is because the contributionType method of ContributionAggregate was removed in -r43570. Using the financialType method instead appears to work properly.

Also, the general functionality and labeling of this filter needs to be updated to reflect user terminology ("Financial Type") and schema changes related to CiviAccounts improvements.