[Python SDK] Unexpected internal endpoints probe on start

[pocesar]

Describe the bug

When creating an Agent instance on Kubernetes, it will fill the logs with deny requests from the NetworkPolicy since it's trying to issue requests to protected and highly sensitive IPs.
It will also try to reach api.ipify.org for no apparent reason.

There should be a way to opt-out from this behavior on _detect_container_ip

Steps to reproduce

1. Go to '...'
2. Run '...'
3. See error

Expected behavior

Screenshots / Logs

Environment

• Control plane version:
• SDK version (if applicable):
• Deployment environment (local, docker, kubernetes, etc.):

Additional context

[AbirAbbas]

Fix is up in #969: the SDK no longer probes the cloud-metadata endpoints or api.ipify.org when a callback URL is configured (constructor callback_url or AGENT_CALLBACK_URL), and there is an explicit opt-out AGENTFIELD_DISABLE_IP_DETECTION=1 for containers with no callback URL at all. Default behaviour with neither set is unchanged. Will close this when it merges.