Add dynamic configs for the spark-rapids IT pipelines (NVIDIA#1450)

Add dynamic spark-rapids configs for the IT pipelines via parameter:
'BASE_SPARK_SUBMIT_ARGS=--conf abc=xxx --conf xyz=xxx --conf def=xxx ...'.

e.g. We can enable spark 'AQE' for spark-rapids integration tests pipeline by:
    'BASE_SPARK_SUBMIT_ARGS=--conf spark.sql.adaptive.enabled=true'

The default value 'BASE_SPARK_SUBMIT_ARGS' is unset

Signed-off-by: Tim Liu <timl@nvidia.com>

jenkins/spark-tests.sh

@@ -67,7 +67,8 @@ OUTPUT="$WORKSPACE/output"
 # spark.sql.cache.serializer conf is ignored for versions prior to 3.1.0
 SERIALIZER="--conf spark.sql.cache.serializer=com.nvidia.spark.rapids.shims.spark310.ParquetCachedBatchSerializer"
 
-BASE_SPARK_SUBMIT_ARGS="--master spark://$HOSTNAME:7077 \
+BASE_SPARK_SUBMIT_ARGS="$BASE_SPARK_SUBMIT_ARGS \
+    --master spark://$HOSTNAME:7077 \
     --executor-memory 12G \
     --total-executor-cores 6 \
     --conf spark.sql.shuffle.partitions=12 \