[SPARK-8861][SPARK-8862][SQL] Add basic instrumentation to each SparkPlan
operator and add a new SQL tab
This PR includes the following changes:
### SPARK-8862: Add basic instrumentation to each SparkPlan operator
A SparkPlan can override `def accumulators: Map[String, Accumulator[_]]` to
[SPARK-8861][SPARK-8862][SQL] Add basic instrumentation to each SparkPlan
operator and add a new SQL tab
This PR includes the following changes:
### SPARK-8862: Add basic instrumentation to each SparkPlan operator
A SparkPlan can override `def accumulators: Map[String, Accumulator[_]]` to