feat: generic client

[driftluo]

This is a major change:

1. Generic client implementation, allowing users to choose their own client and runtime dependencies. reqwest is implemented by default, but can be disabled using a feature. Here's an implementation example.
2. Optimized line protocol implementation, reducing memory allocation frequency.
3. Separated implementations of the Send and non-Send interfaces. Users can implement them as needed; not all implementations are required for use.
4. Currently, chunk query has been truly implemented, returning a Stream type for segmented parsing.

If no one objects, I will merge this PR and release version 0.7 in two days. close #38

[driftluo]

@qwandor Do you have any suggestions for this implementation?

[qwandor]

I haven't fully reviewed the code, but it looks reasonable.