Changes in 0.9.1

gnrc::nib: New module for GNRC neighbor information.
LED: Differentiate constructors, deprecate ::new().
Internally use const { } and other recent Rust idioms suich as c"".
Update dependencies: Rust to 1.79 and the coap-message crate (implementing message upgrading).
Extend tests.

Changes in 0.9.0

These items will require code changes for all who use them.

VFS: Opening directories now takes a pinned slot to store the open directory in.
ZTimer: Sleep functions were renamed for consistency
- sleep() became sleep_extended()
- sleep_ticks() became sleep() and takes Ticks(u32) instead of a plain u32
Support for all outdated traits was removed:
- embedded-hal 0.2 (except for ADC and SPI)
- coap-handler 0.1 and coap-message 0.2
- embedded-nal-async 0.6

These items will only require code changes for users who had unresolved deprecation warnings, or who explicitly named clock or error types.

All deprecated items were removed.
gcoap: PacketBuffer now has a lifetime.
saul: Unit is non-exhaustive.
shell: .and() returns an impl CommandList instead of a Command. This drastically enhances usability because chaining is now possible without extra effort going into type annotations.
ztimer: Clocks are now generated as ValueInThread<Clock<HZ>> and require to stay in a thread to allow using the sleep{,_*} methods.
Traits that previously used ! as associated error type now use Infallible.
Dependencies: heapless is now used in version 0.8. This is a public dependency because saul::Unit::name_owned returns a buffer.

gpio: .toggle() was added.
shell: .run_forever() and .run_once() are now available with provided buffers; the previous …_providing_buf() variants are now deprecated aliases.
ztimer: Timers can be .acquire()'d and then provide a .now() method, as provide a .time() method to measure the execution time of a closure.