* Added `PP+exe:args` syntax
If `PP+exe:args` is specifically given, only it used.
Otherwise, `PP:args` and `exe:args` are combined.
If none of the `PP`, `exe` or `PP+exe` args are given, `default` is used
`Default` is purposely left undocumented since it exists only for backward compatibility
* Also added proper handling of args in `EmbedThumbnail`
Related: https://github.com/ytdl-org/youtube-dl/pull/27723
`to_screen`, `report_warning`, `report_error`, `write_debug`, `get_param`
This is a first step in standardizing these function. This has to be done eventually for extractors and downloaders too