[spark-rapids] generate actions from templates

spark-rapids/mig.sh, spark-rapids/spark-rapids.sh:
* no longer tracking generated action

spark-rapids/test_spark_rapids.py:
* using default machine type of n1-highmem-8
* de-duplicating shell command
* perform two tests on one cluster instead of one test on two

templates/spark-rapids/mig.sh.in,
templates/spark-rapids/spark-rapids.sh.in:
* these templates include only the code unique to these actions

Author: cjac