Optimize toHex function in CommonData.cpp

[reallesee]

Replace incremental index updates with direct assignment when adding "0x" prefix in the toHex function. This eliminates unnecessary increment operations and makes the code more straightforward while maintaining identical functionality

[github-actions]

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[clonker]

Thank you for your contribution! I find your reasoning at the very least debatable:

• the entire function is built on incrementing i, so using direct assignment (albeit known) leads to less consistent code
• if, say, the prefix(-length) changed for whatever reason, the current approach automatically accommodates for that without having to explicitly reset the index
• there is no performance benefit, modern compilers will optimize out the increment

Since this is simply a refactor that doesn't really add anything, I'll go ahead and close this.