[Tests] clearer comparison of HDF5 files

Working on !931 (merged), I found the comparison of HDF5 files against reference files was not very clear. This aims to show all the differences found, not only the first one (i.e. not asserting on each separate step), to present the results in a clearer format, and to simplify the code doing the comparisons.

Based off the branch in !931 (merged), because I know that fails the relevant tests, so I can see what the results look like.

cc @ahmedk

tests/test_reference_runs/conftest.py

@@ -38,15 +38,6 @@ def pytest_addoption(parser):
               "apply validation test on numerical data only."),
     )
 
-    parser.addoption(
-        "--find-difference",
-        action="store_true",
-        default=False,
-        help=(
-            "In case of non numerical validation of h5file. "
-            "Find the different attribute and fail on the first one."),
-    )
-
     parser.addoption(
         "--use-slurm",
         action="store_true",
@@ -80,8 +71,6 @@ def release_test_config(request):
         "--no-numerical-validation")
     validate_only = request.config.getoption(
         "--validation-only")
-    find_difference = request.config.getoption(
-        "--find-difference")
     use_slurm = request.config.getoption(
         "--use-slurm")
     picked_test = request.config.getoption("--picked-test")
@@ -90,8 +79,7 @@ def release_test_config(request):
     return (
         detectors, calibration, picked_test,
         skip_numerical_validation, validate_only,
-        find_difference, use_slurm, reference_folder,
-        out_folder,
+        use_slurm, reference_folder, out_folder,
     )