Support beatmap length filtering with multiple scales

[brandondong]

In the lazer song select menu, you can filter using a query like length<=2m30s. Relevant code: https://github.com/ppy/osu/blob/7cdedfb6ca408b8ace311944bc3bf8b8454c515d/osu.Game/Screens/Select/FilterQueryParser.cs#L342

From what I can tell, this doesn't work in the web search. length<=2m works and length<=30s works but not with the minute and second scales combined (length<=2m30s). I don't think there should be a discrepancy when using the same query but in the web search.