modules: openthread: initialize settings in `otPlatCryptoInit()`

In OpenThread, Settings are initialized after KeyManager by default.
If device uses PSA with emulated TFM, Settings have to be initialized
at the end of otPlatCryptoInit(), to be available before storing
Network Key.

Signed-off-by: Maciej Baczmanski <maciej.baczmanski@nordicsemi.no>