Miscellaneous cleanups in vm.runtime.defmeth tests

In particular:
  - replace test/hotspot/jtreg/vmTestbase/vm/runtime/defmeth/scenarios with enumeration of different test configurations in tests themselves;
  - pass TestBuilder as a parameter and initiate test execution from executor;
  - switch max class file version tested from 52 to 61 (V17);
  - minor changes (cleanups, new test cases)