[RTA/DPA BW tests] Patch for broken BW tests
lhcb/Moore!4035 (merged) had a bug in that the simulation
key was no longer provided in a BW test option file. However, given the TestFileDB is now being used in the test, we should get that key (and some others) from the TestFileDB entry. This MR does that, and also is a little more careful with what configuration is optional and what is required to make us a little more robust.
Testing locally now.