Verification with cross-signing may requiring asking for your secret storage
passphrase, which is displayed in it's own modal on top of flows. For now while
verification takes in modals also, mark the verification ones as static so they
don't lose state when secret storage appears on top mid-flow.
this uses a verification requests as emitted by the js-sdk with
the `crypto.verification.request` rather than a verifier as emitted
by `crypto.verification.start` as this works for both to_device and
timeline events with the changes made in the js-sdk pr.
