feat: ✨ c-family icons improvements

[lucas-labs]

Updates all icons for the C-family of languages so that:

• they look nice together, having a similar style
• the C in C++ doesn't look like a G when looked at 16px

Apart from the changes discused in #2294, I went ahead and also changed C# icon, to have the same shape for the C letter as in the others.

Fixes #2294

[github-actions]

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[PKief]

Thank you for providing a PR so soon! Please have a look at the review comment for the hpp file icon. But except of that your changes look very nice from my point of view.

[github-actions]

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[github-actions]

Merge Successful

Thanks for your contribution! 🎉

The changes will be part of the upcoming update on the marketplace.