feat: asyncio microgen client

[rafilong]

Resolves #73

[tritone]

Generally looks good, a couple questions. Do you have system tests running yet which exercise the async microgen code path?

[BenWhitehead]

Good to merge after addressing @tritone's questions.

[rafilong]

@tritone Unfortunately system tests do not exist yet - I was waiting to complete integration of the client before writing system tests, as I feel as though they are dependent on the entire client being converted to async, and it would be preferable to wait until that point. As this code is being committed to v2-staging rather than master, I feel like this is a reasonable choice.

[tritone]

@tritone Unfortunately system tests do not exist yet - I was waiting to complete integration of the client before writing system tests, as I feel as though they are dependent on the entire client being converted to async, and it would be preferable to wait until that point. As this code is being committed to v2-staging rather than master, I feel like this is a reasonable choice.

Discussed offline, I'm okay with merging this code into the branch before system tests are added.