Spark Connector: Scala 2.13 support

Apache spark included support for scala 2.12 starting in Spark 3.2.

Couchbase spark 3.3.x connector targets Apache spark framework v3.3. However, the version of scala is still at 2.12.

While spark v3.3 and the latest v3.5 release so support scala 2.12 and 2.13, we must include support for scala 2.13 with couchbase scala connector.

This is based on customer requests (see linked) but also because it will be possible for developers to build spark applications using scala 3.x due to compatibility between scala 2.13 and Scala 3.x.

Reference- https://docs.scala-lang.org/scala3/guides/migration/compatibility-intro.html

Related:  Couchbase Scala SDK 1.5 Client supports Scala 2.12 and 2.13.