Add Support HTTP compression

[bgunebakan]

Adds opt-in HTTP compression support to the crate-python driver to reduce bandwidth usage and improve performance for large queries.

Summary of the changes / Why this is an improvement

• Client-side request compression (compress_client, default: True). Outgoing JSON request bodies are gzip-compressed before being sent.
• Server-side response compression (compress_server, default: False). The driver sends Accept-Encoding: gzip, deflate to CrateDB server when it's enabled.
• Compression is skipped for payloads below compress_threshold bytes (default 8192)
• 6 new unit tests covering: compression disabled, compression enabled, below-threshold skip, Accept-Encoding sent/not sent, and default-args behavior.

Small note on threshold default value:

I've changed compress_threshold to 8192 while implementing. I ran a payload-size sweep against both a local CrateDB instance and a CrateDB Cloud cluster (eu-west-1 free tier), measuring round-trip latency with and without gzip compression. I saw benefits of compression when latency included over 8kb on local and 1kb on cloud instances.

Latency can vary based on my network and cluster settings/location. I decided to move on 8kb as a default value for threshold.

Checklist

• Link to issue this PR refers to (if applicable): Fixes Support HTTP compression #700
• Added or Changed code is covered by tests
• Updated documentation & CHANGES.rst