This commit:
- Implements RFC 147: "all functions must be safe"
- Implements RFC 155: "explicit Context parameter"
- Implements the pending breaking change #141: reject assign syntax in `init`
(which was used to initialize late resources)
- Refactors code generation to make it more readable -- there are no more random
identifiers in the output -- and align it with the book description of RTFM
internals.
- Makes the framework hard depend on `core::mem::MaybeUninit` and thus will
require nightly until that API is stabilized.
- Fixes a ceiling analysis bug where the priority of the system timer was not
considered in the analysis.
- Shrinks the size of all the internal queues by turning `AtomicUsize` indices
into `AtomicU8`s.
- Removes the integration with `owned_singleton`.