[mednet.tests] Move tests to single directory

...data/histograms/models/histograms_lwnet_cxr8_default.json

...a/histograms/models/histograms_lwnet_drhagis_default.json

.../histograms/models/histograms_lwnet_drionsdb_expert1.json

...ams/models/histograms_lwnet_drishtigs1_optic_cup_all.json

...ata/histograms/models/histograms_lwnet_drive_default.json

.../data/histograms/models/histograms_lwnet_hrf_default.json

...ata/histograms/models/histograms_lwnet_iostar_vessel.json

...data/histograms/models/histograms_lwnet_jsrt_default.json

...istograms/models/histograms_lwnet_montgomery_default.json

...n/data/histograms/models/histograms_lwnet_refuge_cup.json

...histograms/models/histograms_lwnet_rimoner3_cup_exp1.json

.../histograms/models/histograms_lwnet_shenzhen_default.json

...ion/data/histograms/models/histograms_lwnet_stare_ah.json

...tograms/raw_data/histograms_chasedb1_first_annotator.json

...ion/data/histograms/raw_data/histograms_cxr8_default.json

.../data/histograms/raw_data/histograms_drhagis_default.json

...data/histograms/raw_data/histograms_drionsdb_expert1.json

...tograms/raw_data/histograms_drishtigs1_optic_cup_all.json

...on/data/histograms/raw_data/histograms_drive_default.json

...tion/data/histograms/raw_data/histograms_hrf_default.json