Online training of GNN from solution trajectory

[rickybalin]

This is a feature request to add online training capabilities for the GNN model, specifically for the GNN model from a solution trajectory. It will combine the smartredis, gnn and trajGen plugins.

To do items:

• Add a smartredis client class to the Python GNN training script to be able to load data from DB instead of files only
• Turn the smartredis plugin into a class containing the SmartRedis client pointer and methods for sending data so it can be passed to functions in other plugins
• Add methods to the nekRS gnn class to write the mesh and graph data to the DB instead of writing to file
• Validate correctness of the mesh and graph data read by GNN trainer from DB
• Add methods to the nekRS trajGen class to combine successive time steps into a single array and write it to the DB instead of writing to file