Fix cross-platform plex sync, get episode data using both parent folder and filename

[harshithmohan]

Tested with plex on linux and shoko on windows, but should work the other way also.

• Plex on linux, shoko on windows
  • First replace -> no change, path doesn't have back slashes
  • Second replace -> forward slashes are replaced with back slashes
• Plex on windows, shoko on linux
  • First replace -> back slashes are replaced with forward slashes
  • Second replace -> no change, already has forward slashes
• Both plex and shoko on linux
  • First replace -> no change. Except for extreme cases where the filename somehow has \ which it shouldn't
  • Second replace -> no change
• Both plex and shoko on windows
  • First and second replace -> no change

[harshithmohan]

Closing this after a smol discussion in dev-chat 😔

[Cazzar]

Reverting this, because there's a much more reliable method then that to work out proper paths.