ytdl-sub

[BUGFIX] Fix "File name too long" error when a title is used as a folder name (#1479)

Some presets put the video title into a folder name (not just the file name). The code only shortened the file name, never the folder name. So a title with multi-byte characters (like bold/fancy Unicode, which take 4 bytes each) could make the folder name go over the OS 255-byte limit and crash with OSError: [Errno 36] File name too long.

This fix shortens every folder in the path too, not just the file name, while keeping the file extension. output_directory is left alone so real folders aren't touched.

Added a test with a title made of 4-byte bold Unicode characters.

Relates to #1092, #1189

-- Thanks @Nojyto for the contribution!