Implement pandas ExtensionArray tests for AwkwardArray

[mroeschke]

Here's a small doc reference on how to implement the tests: https://pandas.pydata.org/docs/dev/development/extending.html#testing-extension-arrays

All the tests would be located here: https://github.com/pandas-dev/pandas/tree/main/pandas/tests/extension/base

It covers a good amount of the pandas API surface area, and should ensure most operations with AwkardArray are compatable with the API. Happy to receive feedback if the tests are not well defined in a certain area!

cc @martindurant @douglasdavis

[douglasdavis]

Great thanks for pointing those out 👍

[douglasdavis]

One PR in but leaving this open until we cover more of the surface area