Subdivide Path node

As the name suggests.

This could be implemented as a Subdivide Path node that takes path elements selections as an additional input.

The issue names a proposed Subdivide Path node but no files, tests, or entry points. Start by locating existing path-operation nodes and the handling of path element selections. Done means the node can subdivide selected path elements as an additional input, with appropriate coverage for the new behavior.

索引モデルが issue の本文から書いたものです。