[AGIPD] [PC] various fixes in PC notebooks

Description

This MR fixes several issue in AGID PC notebooks, namely:

• fixing UnboundLocalError for a variable in processing notebook leading to plotting failure,
• fixing retrieval of previous constants to be done for all modules,
• fixing buggy indexing of modules for plotting summary plots.
• changing default concurrency from 16 to a function evaluating number of det. instance modules (same way as for darks).
• fixing error in plotting due to matplotlib upgrade.

How Has This Been Tested?

Testing data and reports available here: /gpfs/exfel/exp/MID/202431/p900465/scratch/rovensky/PC_test/202cells0.5MHz_gs0_20clk Test data for SM: /gpfs/exfel/exp/HED/202430/p900438/scratch/rovensky/pc

Relevant Documents (optional)

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

Reviewers

@ahmedk @jsztuk