Hook timeseries chronix conversion

[RiteshKarki27]

Summary:

This PR introduces a new create_chronics hook that processes CSV files containing load and generator power data and converts them into chronics files suitable for power grid simulation tools. The hook reads normalized active and reactive power values from Load and SGen CSV files, maps them to buses using a grid configuration file, and outputs formatted CSV files (optionally compressed with bzip2).

Features:

• Ability to discover and process multiple Load and SGen CSV files.
• Modification to node type file to allow multiple files to be read and stored in the buffer.
• Mapping elements to buses using a grid configuration JSON file.

Changes:

New files:

• lib/hooks/create_chronics.cpp: Main hook implementation.
• include/villas/hooks/create_chronics.cpp: Hook header.
• etc/examples/hooks/create_chronics.conf: Example configuration file.
• tests/integration/hook-create_chronics.sh: Integration test for hook (current work-in-progress).

Modified files:

• lib/nodes/file.cpp: Modify file implementation to read and store multiple files.
• include/villas/nodes/file.hpp: Modified file header.

@al3xa23