DSP-14569: Move thread utils to DseThreadUtils in dse-analytics-core
DSP-14569: Move thread utils to DseThreadUtils in dse-analytics-core

... and make spark-cassandra-connector depends on dse-analytics-core

We do this because there is currently no common module for all analytics
stuff so it is difficult to share some code like thread utils.

datastax/spark-cassandra-connector,datastax/spark-cassandra-connector