Update all tasks to properly set subject and contexts as required by task-configuration and task-history

Once #508 (closed) is done, we should update all the compute_dynamic_metadata() methods of all the tasks to ensure that:

• they do call their parent implementation (for the handling of shared fields like task_configuration and task_history)
• they do set proper subject, configuration_context and runtime_context in their data

We also update the documentation to document what values are used for subject/contexts.

This concerns Worker tasks, Server tasks and Workflows alike.

(This is required so that we can have proper tracking of historical resource consumption)

Track time in #510 (closed)