msgq: optimize queue size

[adeebshihadeh]

msgq uses a fixed default size for all queues. Since our struct are all different sizes, this leaves some services with only 10s of buffer and others with more than an hour; if left running for long enough, the queues will use up ~400MB. At build time, we know the struct size (except lists) and frequency for all services, so we can set each service's queue size based on buffer time, which should save quite a bit of memory.