Raw sends (api.jmap.sendRaw and submitRaw) now always lose label headers
a plugin wrote while the organisation uses labels. A crypto takeover is
matched to its raw send by a labelToken the composer puts in the
onComposeSend request (plugins that don't pass it back are matched by
identity, and refused when two takeovers are open), not by comparing
subjects. A raw send outside a takeover gets the default label, or is
refused when a label is required. The extra header is folded on the raw
path. The takeover code moves to lib/outgoing/classification-raw.ts;
the old test that let a raw send outside a takeover through unlabelled
now expects the forged header to be removed.