interrupt priority to component mapping?

[sethp]

consider how to name the priority levels assigned to different components (consts, re-export, etc.)

It seems to me like the goals ought to be:

• collecting all the named priorities in a single place, so we can easily answer e.g. "is UART0 or UART1 going to take precedence?"
• making it very easy to re-assign priorities, e.g. "let's raise UART0's priority above UART1's" without violating safety guarantees
  • what might go wrong here? do we have an example change in mind?
• nice to have: the ability to reshape (ideally, transparently to the other modules) the priority system to introduce e.g. fn masking_threshold for a priority (i.e. the next enum element)

what do you think?

Originally posted by @sethp in #15 (comment)