Simplified firmware.bin file check

[tadeubas]

What is this PR for?

At boot, we did a simple firmware check to skip updates if firmware.bin was missing. Later, a full check required firmware.bin but allowed installing a different firmware_X.bin, which made no sense.

Note: we only published firmware.bin, so allowing other filenames made no sense.

Simulator now mocks firmware installation! Just copy the files to "simulator/sd" folder and execute simulator with --sd.

Changes made to:

• [x] Code
• [x] Tests
• [ ] Docs
• [ ] CHANGELOG

Did you build the code and tested on device?

• [x] Yes on Yahboom

What is the purpose of this pull request?

• [ ] Bug fix
• [ ] New feature
• [ ] Docs update
• [x] Other

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 95.35%. Comparing base (8dbd794) to head (d443789). Report is 6 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #587      +/-   ##
===========================================
- Coverage    95.35%   95.35%   -0.01%     
===========================================
  Files           76       76              
  Lines         8619     8615       -4     
===========================================
- Hits          8219     8215       -4     
  Misses         400      400              

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

:rocket: New features to boost your workflow:

• :snowflake: Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[odudex]

Thank you!