Further issues found with the EOL being written to the Database

[john-science]

@albeanth and I identified two places where the ARMI codebase does not support the new EOL time point being written to the database (added in PR 1090):

1. Database3.genTimeSteps():

armi/armi/bookkeeping/db/database3.py

Line 612 in 8b5163a

def genTimeSteps(self) -> Generator[Tuple[int, int], None, None]:

Returns (cycle, node), but if the EOL is present in the DB, it just returns the last time node twice.

2. Database3.load() takes in cycle and node as integers, thus not allowing us to load an EOL timestep:

armi/armi/bookkeeping/db/database3.py

Line 702 in 8b5163a

def load(

[albeanth]

Cross-referencing #1090 since it's related.