Dynamic usages highlighting support

MPS 2020.3 brought support for dynamic usages highlighting. It would be useful to support this in the diagram editor as well, in particular if this can be customized e.g. to highlight the context of a selected node.

Start by locating the diagram editor entry points and reviewing how MPS 2020.3 exposes dynamic usages highlighting. The issue names no files or tests and leaves the customization design open; done would require agreed behavior for highlighting usages, including the context of a selected node, plus coverage for that behavior.

Written by the indexing model from the issue text.