proxy-go is still deadlocking occasionally

The three fallback proxy-go instances are still hanging, after variable delays of a few days. This is even after removing all memory restrictions I discussed in #21312 (comment 2591535).

The more heavily used instances seem to deadlock sooner. Those for the currently used broker would be more likely to stop than those for the standalone broker. But the ones for the standalone broker would stop too.

In the meantime, I've put the fallback proxies back on periodic restarts. Before the intervals were 1h,2h,10h; now I increased them to 17h,23h,29h (prime numbers, so the average time before the next restart is < 17h).

I'll update this ticket with a graph showing uptimes when I have time.