Fixes an issue detected by the fuzzer

[phlptp]

about an out of range string conversion not being caught properly. This commit changes the logic from an exception to using errno and a non-throwing alternative.

Issue detected in
https://github.com/CLIUtils/CLI11/actions/runs/5500247554/jobs/10023032108

The problem string was set up as a test.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (ff648c8) 99.46% compared to head (4ef31c3) 99.46%.

❗ Current head 4ef31c3 differs from pull request most recent head 2c1ada0. Consider uploading reports for the commit 2c1ada0 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #905   +/-   ##
=======================================
  Coverage   99.46%   99.46%           
=======================================
  Files          18       18           
  Lines        4100     4108    +8     
=======================================
+ Hits         4078     4086    +8     
  Misses         22       22           

Impacted Files	Coverage Δ
include/CLI/TypeTools.hpp	100.00% <100.00%> (ø)
include/CLI/impl/App_inl.hpp	99.31% <100.00%> (ø)
include/CLI/impl/Option_inl.hpp	99.75% <100.00%> (+<0.01%)	⬆️

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