bridge: implement MSGQ to ZMQ bridge with subscriber-based publishing

[deanlee]

resolve commaai/msgq#282, Implementing an efficient MSGQ to ZMQ bridge that only publishes services with active subscribers.

Changes:

1. New MSGQ to ZMQ Bridge Implementation: Utilizes ZMQ's socket monitoring to bridge MSGQ services to ZMQ efficiently.
2. Active Subscriber Detection: Only connects to MSGQ services requested by subscribers and publishes events when subscribers are active. Closes the connection to MSGQ if no subscribers are active.
3. Resource Management: Enters a sleep state when no subscribers are available, ensuring minimal overhead and scalability.
4. Always-On Operation: With no overhead when there are no subscribers, the bridge can always run on the car.

This update ensures efficient resource utilization and scalability by dynamically managing connections based on subscriber activity.

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[deanlee]

We need to add a sleep here to reduce CPU usage while polling.
the MSGQ uses SIGUSR1 for notification between publishers and subscribers, resulting in extremely frequent EINTR signals. This interrupts the poll function frequently, leading to a busy retry loop. This can increase CPU usage from an expected 0% to around 4% during the polling period while waiting for subscribers to connect. Other interrupt-driven modules like camerad, sensorsd may face similar issues.

There's also a bug related to the SIGUSR1 signal: even after the subscriber disconnects, msgq's publisher keeps sending signals to the closed subscriber process.

commaai/msgq#617 is a solution. However, it still needs more testing to confirm its reliability.
msqg: use futex for IPC notifications commaai/msgq#625 is a soluton

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[sshane]

@deanlee now PJ streaming looks rather choppy and sometimes skips a split second of data, can you take another look at this?

[deanlee]

@sshane I didn't find issue when reviewing the code. Running zmq=1 ./junggle.py --stream also appears to be normal.Has this problem always been present, or is it intermittent?

[deanlee]

I found the issue.looks like the old bridge has the same issue too.I'll fix it when back to my computer