stream.hls_filtered: refactor tests, use mixin
stream.hls_filtered: refactor tests, use mixin

melmorabity/streamlink,melmorabity/streamlink,gravyboat/streamlink,gravyboat/streamlink,chhe/streamlink,chhe/streamlink,bastimeyer/streamlink,streamlink/streamlink,streamlink/streamlink,beardypig/streamlink,beardypig/streamlink,bastimeyer/streamlink