Initial support for CSMA-CA

[SamClercky]

This PR adds initial support for CSMA-CA.

It adds:

• An implementation for CSMA-CA
• Definitions for multiple traits that are necessary to communicate with real hardware
  • Radio: Abstraction over a physical radio
  • RadioFrame/RadioFrameMut: Abstraction over the representation of a frame that a physical radio requires
  • TxToken/RxToken: To easily (de)construct a frame specifically for a given physical radio
• A way to interact with the CsmaDevice from a higher network layer (Driver trait)
• Some initial testing infrastructure which includes some mocking implementations for the different traits

Additionally this PR includes some bugfixes and extra tests to the concurrency primitives.

Things that still need to be done:

• More CSMA-CA tests
• Configuration options for the CsmaDevice

[codecov]

Codecov Report

Attention: Patch coverage is 90.71481% with 126 lines in your changes are missing coverage. Please review.

Project coverage is 69.45%. Comparing base (ed48f23) to head (899d5d2).

Files	Patch %	Lines
dot15d4/src/phy/config.rs	21.56%	40 Missing ⚠️
dot15d4/src/csma/mod.rs	94.43%	39 Missing ⚠️
dot15d4/src/phy/radio/mod.rs	84.81%	24 Missing ⚠️
dot15d4/src/sync/tests.rs	92.13%	7 Missing ⚠️
dot15d4/src/csma/transmission.rs	90.90%	6 Missing ⚠️
dot15d4/src/sync/channel.rs	95.76%	5 Missing ⚠️
dot15d4/src/sync/mutex.rs	92.45%	4 Missing ⚠️
dot15d4/src/phy/driver.rs	97.61%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #4      +/-   ##
==========================================
+ Coverage   60.68%   69.45%   +8.77%     
==========================================
  Files          27       35       +8     
  Lines        3576     4908    +1332     
==========================================
+ Hits         2170     3409    +1239     
- Misses       1406     1499      +93     

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