fix: apply connection compression option

[skhe]

Summary

• Forward compress_msg=0/1 to the Go driver and report the negotiated compression state through the Python connection property.
• Reject invalid compression values and changes after login.
• Reject explicit use_stmt_pool=1 because the underlying driver does not implement statement caching; accept use_stmt_pool=0.
• Update API documentation and regression evidence.

Validation

• Before fix: compress_msg=1 read back as 0, invalid value 2 and use_stmt_pool=1 were silently accepted.
• Official ARM DM8 UTF-8: 188 passed, 2 deselected, 0 skipped.
• Official ARM DM8 GB18030: 188 passed, 2 deselected, 0 skipped.
• Go bridge: go test ./... passed.