String types conversions as an analyzer + code fix

This code was a refactoring but converted to a code fix after discussion in #93 following the decision of #66.

**Note:** This PR can't be merged as-is as the 2 diagnostics need an ID from https://github.com/code-cracker/code-cracker/wiki/DiagnosticIds . The current next ones are `CC0045` and `CC0046`