Write JRS test for PCES freeze

We should have a JRS test that exercises the following code pathway:

- freeze is scheduled
- network freezes and writes state
- network is shut down
- freeze state is deleted from disk
- network is restarted, it should freeze again and write state to disk

Start by locating the existing JRS tests and the freeze pathway in the consensus node. Run the relevant JRS test suite and trace the scheduled freeze, state write, shutdown, disk deletion, and restart steps. Done means a test verifies that the restarted network freezes again and writes freeze state to disk.

Written by the indexing model from the issue text.