Enable the use of test key or prod key for PKI

[srasoamiaramanana-ledger]

This PR allows to either load a PKI production certificate or a test certificate for testing purposes. By default, speculos will verify the certificate with a test key, one has to launch speculos with the argument --pki-prod/-p to verify a production certificate.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 10 lines in your changes missing coverage. Please review.

Project coverage is 43.83%. Comparing base (fde57e3) to head (b604b73).

Files with missing lines	Patch %	Lines
src/launcher.c	0.00%	4 Missing ⚠️
speculos/main.py	0.00%	3 Missing ⚠️
src/bolos/os_signature.c	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #540      +/-   ##
==========================================
- Coverage   43.86%   43.83%   -0.03%     
==========================================
  Files         125      125              
  Lines       12448    12456       +8     
  Branches      993      994       +1     
==========================================
  Hits         5460     5460              
- Misses       6653     6661       +8     
  Partials      335      335              

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