Optionally derive defmt::Format for some types

[smaeul]

This allows them to be referenced in format strings when using the defmt logging framework. Currently this only covers the smaller enums for things like packet headers and error codes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.90%. Comparing base (609c3a3) to head (7290437).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #48   +/-   ##
=======================================
  Coverage   90.90%   90.90%           
=======================================
  Files          55       55           
  Lines        7456     7456           
=======================================
  Hits         6778     6778           
  Misses        678      678           

Files with missing lines	Coverage Δ
src/mqtt/connection/event.rs	87.50% <ø> (ø)
src/mqtt/packet/packet_type.rs	96.49% <ø> (ø)
src/mqtt/packet/property.rs	96.49% <ø> (ø)
src/mqtt/packet/qos.rs	100.00% <ø> (ø)
src/mqtt/packet/retain_handling.rs	100.00% <ø> (ø)
src/mqtt/result_code.rs	100.00% <ø> (ø)

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[redboltz]

Thank you!
It looks good to me.