Port Flex

[cedelavergne-ledger]

Port the app to support Flex.

This includes:

• Port NBGLv2
• Minor improvements in navigation and About menu display
• Deactivation of the decryption with the curve cv25519 (CV25519 support is broken #84)
• Add Flex config
• Update snapshots

Checklist

• App update process has been followed
• Target branch is develop
• Application version has been bumped

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 27.01%. Comparing base (74e65a4) to head (3a5e42b).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #107   +/-   ##
========================================
  Coverage    27.01%   27.01%           
========================================
  Files            1        1           
  Lines          211      211           
========================================
  Hits            57       57           
  Misses         154      154           

Flag	Coverage Δ
unittests	27.01% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[github-advanced-security]

This pull request sets up GitHub code scanning for this repository. Once the scans have completed and the checks have passed, the analysis results for this pull request branch will appear on this overview. Once you merge this pull request, the 'Security' tab will show more code scanning analysis results (for example, for the default branch). Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results. For more information about GitHub code scanning, check out the documentation.