Cite's MWDocumentReferences included a Document, which caused
auto-save serialization to fail silently on the cyclical reference.
This patch moves the caching to per-instance scope, which was the
better choice to begin with. The document refs are recalculated after
each change anyway, and caching is only necessary to work around an
awkward control flow in which each ReferenceNode is responsible for
its footnote number.
Bug: T377484
Change-Id: Iebe4befd603fe07d9da2a5bb6126228ec4d5dfea
Reverses the previous logic which traversed up from a fragment to get
the full document's refs. Much other code in VE isn't ready for this
behavior, for example we can see list-defined refs but not inline refs
defined outside of the fragment.
This patch will ensure that we're only looking at refs accessible from
the current fragment, and prevents caching on fragments because the
cache uses `persistentStorage`, which is shared between fragments and
their parent document.
Bug: T374068
Change-Id: Ia38098f8b3e5a9d24c2206e11edab37d60209225
