[gem.cbc.ca] Add support for downloading live replay content

[scribblemaniac]

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This PR adds support for downloading livestream events after the event has passed, if on-demand replay is available. An example URL for such a case is: https://gem.cbc.ca/live-event/42314

The download process is the same as CBC Gem live content, but the formattedIdMedia key-value pair is in a different part of the video info, it does not work for me with appCode='mpx', and obviously it is not live.

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[scribblemaniac]

Thanks @bashonly for the review and improvements. Tested and it appears to be working well.