New SDK feature disablers + USB disabler fix with DEBUG builds

[apaillier-ledger]

Description

• Building an app with disabled USB would not work with DEBUG builds since on devices other that the Nano S, the printf implementation uses the USB
• The UI (NBGL or BAGL) can be completely disabled for faster compilation when not needed (Ethereum plugins for example)
• Fixed builds with seproxyhal not enabled + added a disabler for it in the standard_app Makefile
• Breaking change for Stax apps that use the QR code feature without explicitly adding its source path

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)

[codecov-commenter]

Codecov Report

Patch and project coverage have no change.

Comparison is base (d31f67c) 69.09% compared to head (e3f4693) 69.09%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #397   +/-   ##
=======================================
  Coverage   69.09%   69.09%           
=======================================
  Files          11       11           
  Lines         864      864           
=======================================
  Hits          597      597           
  Misses        267      267           

Flag	Coverage Δ
unittests	69.09% <ø> (ø)

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[xchapron-ledger]

CI is failing on many apps :/

[xchapron-ledger]

I' didn't know this exists... this is somehow a duplicate of what's done in lib_standard_app/main.c: common_app_init(). Maybe we can merge?