Figure out why try_read_subscriptions() is so CPU intensive

[techtunde]

This repo was added to our company repo in an effort to add the try_read_subscriptions function to allow an immediately returning polling function for MQTT calls. When testing with vehicle software (which is where this is needed) the CPU usage of each hootl increased dramatically when compared to the existing way of polling MQTT deterministically (using timeout to not wait indefinitely), but this existing way has the potential for data loss.