reiterate on streaming extractor APIs

[Gottox]

Is your feature request related to a problem? Please describe.

One of the pieces where libsqsh isn't zero-copy is the uncompression of non-continious blocks. While this is an edge case it could end up in situation where up to 1 MiB get copied just to uncompress them afterwards and unnecessarily cache them.

Describe the solution you'd like

The better solution is to write the partial blocks to the extractor and let it handle internal state. This would reduce the amount of (large) copies inside libsqsh.

Describe alternatives you've considered

None

Additional context

The issue is that the implementation of extractors must be capable to always process incoming data completely.