Feat: Add classes and objects to enable PANGEA support

[chalmerlowe]

WIP: do not merge.

Internal reference: b/358215039

[conventional-commit-lint-gcf]

🤖 I detect that the PR title and the commit message differ and there's only one commit. To use the PR title for the commit history, you can use Github's automerge feature with squashing, or use automerge label. Good luck human!

-- conventional-commit-lint bot
https://conventionalcommits.org/

[Linchin]

Thank you for working to add PANGEA support! It's great that I can do a quick review early to make sure we are on the same page. I think the approach looks good, but I left a few comments on implementation details.

Also, before generating the rest, I think it'd be helpful to add tests to ensure the current code is working as intended.

[chalmerlowe]

Thank you for working to add PANGEA support! It's great that I can do a quick review early to make sure we are on the same page. I think the approach looks good, but I left a few comments on implementation details.

Also, before generating the rest, I think it'd be helpful to add tests to ensure the current code is working as intended.

Tests are next on my list for this first batch of classes.
With some proof of concept classes and tests in hand, we should be able to move on and add the remaining classes.

[suzmue]

Thanks for making the changes! I think this update looks really good.