unstreamIntoM improvements

[lehins]

massiv/massiv/src/Data/Massiv/Vector/Stream.hs

Lines 263 to 274 in c07f147

	unstreamIntoM ::
	(Mutable r Ix1 a, PrimMonad m)
	=> MArray (PrimState m) r Ix1 a
	-> Size
	-> S.Stream Id a
	-> m (MArray (PrimState m) r Ix1 a)
	unstreamIntoM marr sz str =
	case sz of
	Exact _ -> marr <$ unstreamMaxM marr str
	Max _ -> unsafeLinearShrink marr . SafeSz =<< unstreamMaxM marr str
	Unknown -> unstreamUnknownM marr str
	{-# INLINE unstreamIntoM #-}

Either improve unstreamIntoM or add a separate function that can also:

• return the number of elements that have been loaded
• grow the array with Max and Exact sizes as well, if the mutable target doesn't have enough