Moved mc_ch_in_pc configs to data

pyproject.toml

src/ptbench/configs/datasets/mc_ch_in_pc/__init__.py

src/ptbench/configs/datasets/mc_ch_in_pc/default.py

src/ptbench/configs/datasets/mc_ch_in_pc/rgb.py

src/ptbench/data/mc_ch_in_pc/__init__.py

src/ptbench/data/mc_ch_in_pc/default.py

src/ptbench/data/mc_ch_in_pc/rgb.py