Check for `unknown variant` on to-device sending and fall back to room event encryption. (#4847)

* Check for `unknown variant` on to-device sending and fallback to room event encryption.

* fix tests

* fix error js-sdk api type

* Change logger from debug to warn for unsupported to-device transport and improve error message comments

* also add case for not supported
This will be send by the driver in case we sent an encrypted to-device but do not have support of that.

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Co-authored-by: Robin <robin@robin.town>