Update CassandraIO to use the cassandra driver 4.x.x

Cassandra driver was updated to version 4 to get rid of Guava and improve its API. Notice that the 4 in the version is not the version of the server it supports, the driver is fully compatible with Cassandra versions bigger than 2.1

There is a migration guide here:
https://github.com/datastax/java-driver/tree/4.0.0/upgrade_guide
This can have effects on CassandraIO public API we need to measure the impact of this too. However remember that the public API is still `@Experimental`

Imported from Jira [BEAM-6911](https://issues.apache.org/jira/browse/BEAM-6911). Original Jira may contain additional context.
Reported by: iemejia.