fix(lens): canon lens detecton should be independent of locale

[hassec]

• replace std::stof by a locale independent string-> float alternative.
• Run the lens tests a 2nd time in the CI with a DE locale to protect against regressions. This only protects locale based regressions in the canon lens detection. But exiv2 could probably benefit from a more global test. Something for the exiv2 maintainer team to consider.

Closes #2746

[codecov]

Codecov Report

Attention: Patch coverage is 68.75000% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 64.57%. Comparing base (b6e1360) to head (6565352).
Report is 1 commits behind head on main.

Files	Patch %	Lines
src/canonmn_int.cpp	68.75%	1 Missing and 4 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2938   +/-   ##
=======================================
  Coverage   64.57%   64.57%           
=======================================
  Files         104      104           
  Lines       22196    22207   +11     
  Branches    10882    10889    +7     
=======================================
+ Hits        14332    14341    +9     
- Misses       5622     5623    +1     
- Partials     2242     2243    +1     

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