Map and IntMap updateLookupWithKey have different behaviors

[meooow25]

Data.Map.updateLookupWithKey and Data.IntMap.updateLookupWithKey have different behaviors on replacement.

containers/containers/src/Data/Map/Internal.hs

Lines 1121 to 1123 in 32c80d8

	-- | \(O(\log n)\). Lookup and update. See also 'updateWithKey'.
	-- The function returns changed value, if it is updated.
	-- Returns the original key value if the map entry is deleted.

containers/containers/src/Data/IntMap/Internal.hs

Lines 988 to 991 in 32c80d8

	-- | \(O(\min(n,W))\). Lookup and update.
	-- The function returns original value, if it is updated.
	-- This is different behavior than 'Data.Map.updateLookupWithKey'.
	-- Returns the original key value if the map entry is deleted.

This really bothers me, but I don't think we should change one of them to be like the other because it could introduce a subtle bug for existing users.

Hackage Search (https://hackage-search.serokell.io/?q=updateLookupWithKey) indicates that most users are using it as updateLookupWithKey (\_ _ -> Nothing), which means they want to delete an entry and get the deleted value. This suggests that it would be useful have a function for that purpose.
But even if we add that, we can't get rid of updateLookupWithKey because there is a lot of code out there using the function. The two implementations have been around since the very beginning (bbbba97).

Maybe we just have to live with it.