[Feature] Add support for streamId selection

[i-dentify]

Copied from jonathansant/Orleans.Streams.Kafka#41

Hi,

The using of the message key as stream Id lacks of flexibility, so it could be better to make possible to implement your own stream id selector. A default stream id selector is added with the previous functionality to work with the message key.

[i-dentify]

Work is being done in branch feature/add-support-for-stream-id-selector

Integration tests will be refactored to use the testcontainers package in order to remove the necessity of having a local kafka broker running