Add benchamrk/dataset checkers/validators

[knc6]

• Whether the benchmark has entries for all the keys in the dataset
• If the new benchmark already exists, e.g. a user just uploads the example alignn exfoliation energy as a new benchmark name
• Avoid property name duplication, for example formation_energy_peratom should be in dft_3d dataset only and not in say hmof dataset to avoid any conflict
• Mixing accuracies say MAE and ACC e.g. for bandgap models