fix: network reliability improvements

[abelanger5]

Adds improvements to network reliability including:

• Rejected heartbeats will automatically trigger a new connection request. Heartbeat rejections are a signal that either the engine is down or there isn't a listener established from the worker.
• Sets the following channel options to match the implementation of the Typescript SDK:

channel_options = [
        ("grpc.keepalive_time_ms", 10 * 1000),
        ("grpc.keepalive_timeout_ms", 60 * 1000),
        ("grpc.client_idle_timeout_ms", 60 * 1000),
        ("grpc.http2.max_pings_without_data", 5),
        ("grpc.keepalive_permit_without_calls", 1),
    ]

• Shifts heartbeat to the main thread with an async implementation, which is necessary to interrupt asyncio event flags (which aren't multithreaded)