[Feature request]: Refactor atomic data into joint module

[laserkelvin]

Feature/behavior summary

For a better user/developer experience, we should aggregate all of the various atom featurization methods into a single module.

Request attributes

• Would this be a refactor of existing code?
• Does this proposal require new package dependencies?
• Would this change break backwards compatibility?
• Does this proposal include a new model?
• Does this proposal include a new dataset?
• Does this proposal include a new task/workflow?

Related issues

No response

Solution description

There are a few functions already contained in datatsets.utils (essentially the periodic table), which could get plucked into an datasets.atomic_data module. Another function that could get placed here is from MACE, which has the free ion energy table.

Additional notes

No response