Tool discovery should not be limited to a single traversable navigable

[domfarolino]

Right now, getTools() retrieves tools from all documents underneath one's traversable navigable, i.e., top-level frame tree. This excludes tools from openers and opened documents, i.e., other documents in the browsing context group, and it probably shouldn't. Within a given browsing context group, we should probably collect tools from all top-level browsing contexts, including auxiliary top browsing contexts.

[bvandersloot-mozilla]

I would find this surprising. Particularly if the modelContext is bound to the document.