Update AA scripts after enso-bc fix implementation

[AmineBarkaoui]

This PR implements the necessary changes after the fix implemented in hip-analysis/hip/analysis/analyses/drought.py (see #103).

More specifically:

• The start_monitoring parameter has been created in order to identify the month when we start monitoring the forecasts
• The end_season parameter has been replaced by start_monitoring in the run_bias_correction calls in the operational and analytical scripts
• The inspect-operational-steps notebook has been edited to reflect the fix in hip-analysis
• Less in relation to this, the merge-spi-dryspell-gt-nrt has been updated and cleaned up
• The operational_prism notebook has been created also to add the components related to the saving of the PRISM-readable csv