[TEST] Update AGIPD tests with xray-gain, add DSSC, ePix100 tests and update reference folder path

Description

The AGIPD tests are testing common-mode, rel-gain, offset, and blc only.

As xray-gain correction is missing I want to change this and apply xray-gain as well.

• Update AGIPD correction tests with xray-gain
• Update reference folder based on this issue: https://git.xfel.eu/calibration/pycalibration/-/issues/85

How Has This Been Tested?

It is expected the tests will fail and this MR should lead to updating the reference data that we compare against.

I will do that as a last step after I get an LGTM and before I click merge.

I have already updated it until release 3.11.5

Relevant Documents (optional)

Types of changes

• Test (additional or refactored tests)

Checklist:

Reviewers

@roscar @schmidtp @kluyvert