Fix various small bugs and ToDos

[flo12356]

Added FIXME for still open issues and changed the following values/fixed bugs:

• Blake2s key endianness to big endian
• Increased edu heartbeat safetyFactor to 4
• Increased eduBootTimeMargin

[codecov-commenter]

Codecov Report

❌ Patch coverage is 33.33333% with 20 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.28%. Comparing base (306871d) to head (8f2a8f7).

Files with missing lines	Patch %	Lines
Sts1CobcSw/RfProtocols/FileTransferTimer.cpp	0.00%	20 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #487      +/-   ##
==========================================
- Coverage   90.53%   90.28%   -0.25%     
==========================================
  Files         120      121       +1     
  Lines        6748     6771      +23     
  Branches      320      324       +4     
==========================================
+ Hits         6109     6113       +4     
- Misses        639      658      +19     

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