SCORU/Node: allow to specify kernel logs file for simulation

Context

This MR adds a new optional field to the input of the /global/block/<block_id>/simulate RPC:

"log_kernel_debug_file" : "path"

to specify a file in which to write kernel debug logs. The file is created in <data-dir>/simulation_kernel_logs/. When this field is not set, no logs are written to disk during simulation.