Add PoS blockprod functional tests

[alfiedotwtf]

Currently, all of the Python functional tests in test/functional are PoW-based.

This fix will add PoS tests to the Python functional tests.

• Update RegTest Genesis to include PoS pools using fixed staking and VRF keys #1016
• Include PoS NetUpgrades in RegTest when specified from the command line #1021
• Add Blockprod functional tests #1039
• Add RegTest RPC methods for Genesis values #1040
• Create command line arguments to set genesis staking keys, VRF keys, and pool Id #1092

This is part of #1013

[alfiedotwtf]

I originally had a task to create command line parameters to set genesis staking keys, VRF keys, and pool Id, but after looking at the config code again, I think it will be better to add getter API calls to test-rpc-functions/ RPC.

Edit: on second thoughts, why not both