Unicode file names stripped down

This might be related to #1330.

1. Upload image файл_2.jpg
2. Drag and drop it to page body
3. The first issue: the file name in link will appear as %D1%84%D0%B0%D0%B9%D0%BB_2.jpg instead of файл_2.jpg.
4. And finally, the image is not going to work on front page because all unicode characters are stripped down. The link to image will appear as /blog/first/_2.jpg

Even if I manually change the filename in page editor to файл_2.jpg - this still results "_2.jpg" on front-end.

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PHP Version 7.2.13, Admin Panel v1.9.4

Reproduce the upload and drag-and-drop flow with the Unicode filename файл_2.jpg, then inspect how the admin page editor stores and renders that filename. Compare the generated link and front-page image URL with the expected Unicode filename, and verify both remain usable after the fix.

Written by the indexing model from the issue text.