Modal product updates: static IP proxies, Slack integration, live usage dashboard and GPU fallbacks

Modal shipped static IP proxies that route outbound traffic through workspace-exclusive IPs, plus a native Slack integration for real-time app alerts and a live usage dashboard tracking resources across all workspace apps. The update also adds GPU fallbacks for functions, expanding the pool of resources a function can be scheduled on, and client changes including `modal shell` container IDs and memory snapshotting for parametrized functions.