Restrict context-driven blocks to a wp-curate ancestor

### Description

When the **wp-curate/post** and **wp-curate/post-title** blocks are inserted outside of a query context the blocks fall back to using the global `post`. We should restrict where these blocks are allowed to be inserted by declaring `wp-curate/query` as their block.json `ancestor`.

Additionally, imagining a scenario in which the **wp-curate/subquery** block needs to sit inside a design block, the subquery block should be updated to list **wp-curate/post** as an `ancestor`, rather than a `parent`.

### Use Case

To avoid confusion, certain wp-curate blocks should not be available for insertion outside the **wp-curate/query** block structure.