This will allow a client to determine the provenance of a note they detect,
which might or might not have been created by a particular transaction. Without
this data, it's difficult for a client to determine the source of the notes
they detect, even if they download a full block, because some notes are created
as a result of chain-wide logic, rather than any particular transaction in the
block.

This commit does not yet add this information into the `NoteRecord`s in the
view service, but that's the next step.

Co-Authored-By: Aubrey Dyer <aubrey@penumbra.zone>