chore: migrate to main branch

[dandhlee]

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:

• Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
• Ensure the tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

Fixes #174 🦕

[parthea]

One observation, otherwise LGTM.

[dandhlee]

Please take a look!

[dandhlee]

@parthea I think there's an interesting relationship between "if sample files are touched we'll add Samples tests" and "there aren't enough sample files touched so I won't run these presubmits". I've been manually triggering these but might be worthwhile investigating why they're not getting automatically triggered.