Elastic support for aio-cassandra

**Is your feature request related to a problem? Please describe.**
I am using aio-cassandra in my asyncio based application. Now that I have integrated my app with the aio-cassandra library I don't see the logs instrumentation for it.

**Describe the solution you'd like**
Similar to aiopg and asyncpg, there should be instrumentation for aio-cassandra as well

**Describe alternatives you've considered**
N/A

**Additional context**
async libraries are getting much popularity and these should be added for a popular apm solution like elastic.
aio-cassandra: https://github.com/CharAct3/aiocqlengine

Start by examining the existing aiopg and asyncpg instrumentation, then review the aio-cassandra project linked in the issue to understand its API. Done means aio-cassandra receives comparable Elastic APM instrumentation for its asynchronous database activity, with coverage matching the established integrations.

Written by the indexing model from the issue text.