Add qualifier to Sony's Siren tag

The bulk update request #15609 has been approved by @evazion.

rename siren -> siren_(video_game)

The tag for the horror game Siren lacks any qualifier, despite other tags such as "siren (mythology)" do have one. So I think it should be added to avoid confusion.

The bulk update request #15609 (forum #235359) has been rejected by @evazion.

The bulk update request #15724 has been approved by @evazion.

rename siren_(video_game) -> siren_(series)

I'll do Siren (series) and create Siren 1, since there's a Siren 2 and all current Siren 2 posts are tagged Siren, so it was more of a series tag than a tag for the first game.

The bulk update request #15609 (forum #235359) has been approved by @evazion.

The bulk update request #15724 (forum #235964) has been approved by @evazion.