To facilitate refactoring checks to use the per-node cache from T415297, we want generic functionality available to handle the following:
- checking paragraph-by-paragraph
- caching the results of each paragraph on a per-node basis (so they persist even during editing, unless this paragraph is modified)
- filtering to show actions only for modified paragraphs
- filtering to show actions only for ranges that have not been dismissed
We will achieve this by creating a mixin class called ContentBranchNodeCheck.