Move remaining benchmarks from Scala 2.12 to Scala 2.13

[farquet]

Opening to keep track of benchmarks still stuck on Scala 2.12.

As of Spark 3.2.0, Scala 2.13 is now supported: https://spark.apache.org/releases/spark-release-3-2-0.html

Should be eventually migrated from 2.12 to 2.13:

• [x] apache-spark benchmarks (#327)
• [ ] reactors
• [x] neo4j-analytics (#422)
• [ ] scala-stm-bench7 and philosophers
• [x] finagle-http and finagle-chirper (#328)

[lbulej]

With neo4j-analytics, the problem is the Cypher component of Neo4j (https://github.com/neo4j/neo4j/issues/12687) that keeps it chained to Scala 2.12.

[lbulej]

With neo4j-analytics done (#422), we have just 3 benchmarks (in 2 modules) left.