JavaClient stream response body using byte arrays

[alex-james-dev]

• Currently, JavaClient streams the HTTP response body one byte at a time; this is slow. Make JavaClient stream the HTTP response body using byte arrays; this is faster. Each byte array can contain up to 4096 bytes.

• If none of the HTTP response body bytes are available without blocking, let the worker isolate's event loop run.

• Generate bindings for java.io.BufferedInputStream using jnigen.

• Create a BufferedInputStream from the HTTP response body InputStream to improve performance.

Context

This is a PR for the java_http GSoC '23 project 🌞.
Relevant tracking issue: #957.

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[alex-james-dev]

I renamed the PR title to be <= 50 characters 😄

[alex-james-dev]

I've done a bit of refactoring to try to clean the code up a bit:

• Renamed some variables.

• Rewrote the while loop condition so that it fits on one line.

• Created an extension method for converting from JArray<jbyte> to Uint8List.

The PR is now ready for review! 🎉

Thank you!