src: improve SSL version extraction logic

[gireeshpunathil]

The openssl version as defined in ssl libraries is complex. The current logic to extract the major.minor.pacth format uses C semantics to loop through the text and search for specific patterns. Use C++ string to tidy it up.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines