Consider replacing aiofiles with a different package

[Archmonger]

Description

We currently rely on aiofiles for async file reading, but it may not be the most performant option.

We will need to do some benchmarks and determine whether it should be replaced with aiofile,anyio, or asyncio.to_thread.

[Archmonger]

I've created some benchmarks and it appears that asyncio.to_thread is the most performant under the majority of scenarios.

• Ref: Add performance benchmarks to the readme mosquito/aiofile#88 (comment)