rename data to structures (#1854)

mmseg/apis/inference.py

mmseg/datasets/transforms/formatting.py

mmseg/engine/hooks/visualization_hook.py

mmseg/models/decode_heads/decode_head.py

mmseg/models/decode_heads/stdc_head.py

mmseg/models/segmentors/base.py

mmseg/structures/__init__.py

mmseg/structures/sampler/__init__.py

mmseg/structures/sampler/base_pixel_sampler.py

mmseg/structures/sampler/builder.py

mmseg/structures/sampler/ohem_pixel_sampler.py

mmseg/structures/seg_data_sample.py

mmseg/utils/set_env.py

mmseg/utils/typing.py

mmseg/visualization/local_visualizer.py

tests/test_data/test_seg_data_sample.py

tests/test_datasets/test_formatting.py

tests/test_engine/test_visualization_hook.py

tests/test_evaluation/test_citys_metric.py

tests/test_evaluation/test_iou_metric.py