Refactor fix_file_limit to fix_byte_limit

[dwaris]

Why

• Most filesystems use 255 bytes as the max filename length. The current fix_file_limit function however, will not work on Linux because it's using the length in characters.
• We should use the byte size for cross-platform compatibility.

What Changed?

Refactor of fix_file_limit to fix_byte_limit.

• Use UTF-8 for cross-platform compatibility.
• If name is too long, truncate it!
• We call the function at album, title and playlist creation. No need to iterate over every folder in relative path, we already checked them at creation.
• Fixes issue Songs with weird/long names don't save properly #6

[Dniel97]

Nice work! You are correct a byte size limit is way better than the character limit. I didn't bother with it really because I mainly use macOS and Windows so that's not an issue there.

Thank you for the contribution.