[Snippets-C++] fix a snippets and update another.

[majvax]

Description

Find-non-repeating-number

• Fixed a missing lib
• Fixed const-correctness

Binary-to-decimal-conversion

• Adapted it to c++ as it wasn't using any c++ features.
• Fix few problem related to integer size, using c++20 concept, now support only unsigned integral type and up to 64bit long string

Type of Change

• ✨ New snippet
• 🛠 Improvement to an existing snippet
• 🐞 Bug fix
• 📖 Documentation update
• 🔧 Other (please describe):

Checklist

• I have tested my code and verified it works as expected.
• My code follows the style and contribution guidelines of this project.
• Comments are added where necessary for clarity.
• Documentation has been updated (if applicable).
• There are no new warnings or errors from my changes.