Stabilize `Iterable` arg for collections APIs

[kt3k]

We should stabilize the following APIs in std/collections, and merge them to stable counterparts

• (unstable) chunk
• (unstable) dropLastWhile
• (unstable) dropWhile
• (unstable) intersect
• (unstable) sample
• (unstable) slidingWindows
• (unstable) sortBy
• (unstable) takeLastWhile
• (unstable) takeWhile
• (unstable) withoutAll