ENH: rename protected UList size(label) -> setAddressableSize(label)

- modification/continuation of 8d63073b and 5c1ec7ec (#595).

  Although this protected function is only used internally, the name
  `size(label)` is too easily confused with `resize(label)` and
  `setSize(label)`. The longer method name eliminates some ambiguity.
  Name consistent with PtrListDetail.

- leave size(label) method (for possible compatibility),
  but mark as deprecated

STYLE: more consistent use of resize vs setSize in DynamicList

- more consistency between DynamicList and DynamicField