[chore] Add integration test for sync/async support

[nwithan8]

Description

• Add integration tests verifying that asynchronous functions can be run synchronously via multiple methods (re: [Bug]: Deadlock when blocking on async methods #499)
• Add VCR, associated utilities for integration test suite

Testing

• New integration tests, cassettes for async/sync tests

Pull Request Type

Please select the option(s) that are relevant to this PR.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Improvement (fixing a typo, updating readme, renaming a variable name, etc)

[Justintime50]

Nice work! Love extra tests to verify various usage patterns