Epic: openeo-aggregator Packaging

[soxofaan]

The openeo-aggregator started as a proof-of-concept implementation of a federation component for the openEO Platform project. Multiple steps have been and are being set to deploy this in other contexts. This requires some refactoring/restructuring to properly decouple it from old assumptions.

This is an epic trying to group together other tickets and discussions related to making openeo-aggregator a fully decoupled and reusable component

Internal project tickets:

• Migrate AggregatorConfig to OpenEoBackendConfig config system #112
• Non-public config system #94
• Improve build procedure #97
• Move docs from README to docs folder #108
• Integration tests #63
• Integration tests with processing #113
• Switch to pyproject.toml  #116
• refactor concrete configs out of openeo-aggregator #117
• Bump python requirement #127
• Start EOEPCA 'federated orchestrator' documentation repo #142
• refactor Dockerfile out of generic openeo-aggregator repo #143
• Publish properly on PyPI #146

External project tickets:

• slim down essential openeo-python-driver dependencies openeo-python-driver#296
• Eliminate hardcoded VITO references and resources openeo-python-driver#275
• push releases to PyPI openeo-python-driver#252