Making dot15d4 no_std and Embassy compatible

[SamClercky]

Initial work on #7. This PR includes:

• Decoupling of tracing
• CI test to check that crate stays compatible with no_std and no_alloc

Fixes: #7

[thvdveld]

You need to add a licence to ensure_no_std (the same as all the rest).

I think it's better to remove ensore_no_std from the workspace in Cargo.toml, and just add a job in CI that tries to compile it. Try to compile it for thumbv7m-none-eabi, as this is the target for the nRF52840.

Could you also rename ensure_no_std to ensure-no-std?

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 23 lines in your changes are missing coverage. Please review.

Project coverage is 59.99%. Comparing base (1647135) to head (ceca885).

Files	Patch %	Lines
dot15d4/src/frame/ie/nested.rs	0.00%	23 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #8      +/-   ##
==========================================
+ Coverage   59.91%   59.99%   +0.08%     
==========================================
  Files          31       31              
  Lines        3622     3617       -5     
==========================================
  Hits         2170     2170              
+ Misses       1452     1447       -5     

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