[client] Refactor helpers to expose encapsulated and tested components for building collectors

[antoinemzs]

Proposed changes

• Refactor pyobas to expose more encapsulated utilities to accelerate building of OpenBAS collectors
• Backwards compatibility with legacy helpers

Related issues

• Contributes Rework Tanium Threat Response collector to work with process name signature collectors#86
• Contributes Collector for CrowdStrike Falcon Next-Gen SIEM collectors#68

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality
• I wrote test cases for the relevant uses case
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality

Further comments

Main features:

• Migrate configuration logic into its own submodule; refactor the legacy OpenBASConfigHelper to use this new module
• Migrate collector setup and run logic into its own submodule; refactor the legacy OpenBASCollectorHelper to use the new modules
• Create a new submodule specifically to handle Expectations coming from the API to give them a behaviour. Existing collectors have to manipulate data classes and be tightly coupled to various API endpoints to fetch or update them. With new encapsulation we can hide this behaviour and expose a minimal interface to clients.
• Migrate matching logic to expectations. Not all existing mathcing logic was moved though as it is not used by our collectors (it's unclear whether undisclosed third party collectors have been relying on the part that wasn't migrated, although it had been written for an internal need that did not eventually manifest)

An example collector may be built this way:

from pyobas.daemons import CollectorDaemon
from pyobas.configuration import Configuration

def do_work(collector):
    # get expectations
    expectations = collector.api.inject_expectation.expectations_models_for_source(collector.get_id())
    # get some alerts
    alerts = get_alerts_from_integration_api()
    # do matching work
    match_alerts(alerts, expectations)


if __name__ == "__main__":
    config_hints={
        # API information
        "openbas_url": {"env": "OPENBAS_URL", "file_path": ["openbas", "url"]},
        "openbas_token": {
            "env": "OPENBAS_TOKEN",
            "file_path": ["openbas", "token"],
        },
        [...]
    }

    CollectorDaemon(
        configuration=Configuration(
            config_hints=config_hints
        ),
        callback=do_work
    ).start()

[Dimfacion]

LGTM but I'm no python expert so if someone else wants to chime in, it might be better ...