Support parsing youtube.com/{live,shorts} URLs shared from other apps

[peat-psuwit]

YouTube now use the new format for live streams and shorts. The pattern
is https://www.youtube.com/{live,shorts}/<video id>. But other than
pattern change, the video ID is otherwise completely compatible with the
old format.

Since this pattern is similar to https://youtu.be/ format, re-use that
code by re-shuffle the conditions a bit. The change is applied to both
default and Invidious plugins.

Fixes: #966

[MoojMidge]

@peat-psuwit - plugin.video.youtube supports loading a variety of different YouTube urls using the following plugin url format
plugin://plugin.video.youtube/uri2addon/?uri=PERCENT_ENCODED_ORIGINAL_YOUTUBE_URL

All you would need to do is check whether the host ends with youtube.com or youtu.be (there are other hosts that are used and supported, but those two would cover the majority of shared urls), and then send the original url as a percent encoded value using the uri2addon plugin endpoint.

This allows a number of additional urls (channels/users, clips, embeds, etc.) to be supported, including shorts and live streams, without needing to parse the url in Kore.

[peat-psuwit]

@MoojMidge's idea is now implemented in #1019. Closing this PR in favor of that one. Thank you.