[YouTube Livestream] Remove access time from %(title)s template argument and move to new template argument (e.g. %(access_time)s)

[AlphaCentauri]

Checklist

• I'm reporting a feature request
• I've verified that I'm running youtube-dl version 2021.06.06
• I've searched the bugtracker for similar feature requests including closed ones

Description

Current functionally for downloading a YouTube livestream formats the %(title)s template argument with the time (in the system's local timezone) the stream was accessed by youtube-dl, appending it to the end of the stream's actual title (confirmed by #29293).

This date string does not exist in a livestream's title so it does not make sense to have it attached to the same template argument. For the purposes of video archival this should be moved to its own template argument.

I have [YouTube Livestream] added to the title, but I assume this functionality exists for all extractors, my request would apply to youtube-dl as a whole.