Properly surface non-serializable errors in tests

[sangaline]

AVA runs tests in separate processes, and it uses IPC to communicate them back to the main process for logging and reporting. If an error isn't serializable, then the IPC fails and we end up not being able to see the actual error or even what test failed which is as delightful as it sounds. The main culprit of this has been Axios when there's a Nock error.

This PR improves the situation by adding an Axios response interceptor and sanitizing any errors so that they're serializable. The heavy lifting on the sanitization is done by the serialize-error package which I've added as a dev dependency. It cleans up issues like functions, buffers, and circular references which are the common culprits of non-serializability.

If you want to test this yourself, you can remove fixtures with rm test/fixtures/sdk.test.ts.json and then run npm run test to run the tests. You'll get the opaque error on main and the real error on this branch.

[katiemckeon]

Adding a dev dependency is pretty lightweight and 100% justified here. New code in test/utils/makeAxiosErrorsSerializable.ts is well documented the code makes sense.

Looks good to me.