REF: remove internal Block usage from FrameColumnApply
In the `apply` code, there is still one case where we are directly using the internal blocks. This moves that to a method on the manager, so we don't have to interact directly with the blocks (which ideally we don't want outside of the internals, and let's ArrayManager cleanly support this as well). 

For the rest it still updates the Series' values in place, preserving the performance trick.

cc @jbrockmendel @rhshadrach 
small comments, otherwise LGTM