Add sending of automatic error response when exiting an app while an APDU is not answered yet

[nroggeman-ledger]

Description

The goal of this PR is to add automatic sending of error response when exiting an app while an APDU is not answered yet, if using app_exit() function provided by the SDK (standard app).
Applications have to be modified to switch from os_sched_exit(-1) to app_exit() to exit and return to OS

Changes include

• Bugfix (non-breaking change that solves an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)
• Tests
• Documentation
• Other (for changes that might not fit in any category)

Breaking changes

Please complete this section if any breaking changes have been made, otherwise delete it.

Additional comments

Please post additional comments in this section if you have them, otherwise delete it.

Auto cherry-pick in API_LEVEL

If requested to port the commits from this PR on a dedicated API_LEVEL branch,
select the targeted one(s), or add new references if not listed:

[ ] TARGET_API_LEVEL: API_LEVEL_24
[x] TARGET_API_LEVEL: API_LEVEL_25

This will only create the PR with cherry-picks, ready to be reviewed and merged.

Remember:

• The merge will ALWAYS be a manual operation.
• It is possible the cherry-picks don't apply correctly, mainly if previous commits have been forgotten.
• In case of failure, there is no other solution than redo the operation manually...

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 62.41%. Comparing base (8413395) to head (4fcd786).
⚠️ Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1289   +/-   ##
=======================================
  Coverage   62.41%   62.41%           
=======================================
  Files          14       14           
  Lines        1868     1868           
=======================================
  Hits         1166     1166           
  Misses        702      702           

Flag	Coverage Δ
unittests	62.41% <ø> (ø)

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[tdejoigny-ledger]

@nroggeman-ledger as discussed I think that we need to investigate a bit deeper before merging