Prepare megolm.js for async
Prepare megolm.js for async

Make internal methods of megolm.js ready for asynchronous olmdevice

matrix-org/matrix-js-sdk,matrix-org/matrix-js-sdk,matrix-org/matrix-js-sdk,krombel/matrix-js-sdk,krombel/matrix-js-sdk,matrix-org/matrix-js-sdk,krombel/matrix-js-sdk