APEx benchmarks: add regression test

[JeroenVerstraelen]

Add regression tests to the initial benchmarks.

• To generate reference data, run benchmark once
• Upload reference data to s3 object storage
  • What endpoint/bucket?
• From then on every benchmark run should also compare its output to the reference data
• Alerting when output does not match?
  • For the UDP owner, openEO team?
  • How to configure?
• Save comparison result (Success, failure) to s3 object storage
  • So we can see a timeseries for each benchmark
  • Which endpoint/bucket?

Requirements:

• Should be easy to update reference data.
• Component that we can reuse in our own integrationtests.
• Mostly via configuration, try to avoid having to write custom code for every scenario.