[HUDI-4018][HUDI-4027] Adding integ test yamls for immutable use-cases. Added delete partition support to integ tests (#5501)

- Added pure immutable test yamls to integ test framework. Added SparkBulkInsertNode as part of it.
- Added delete_partition support to integ test framework using spark-datasource.
- Added a single yaml to test all non core write operations (insert overwrite, insert overwrite table and delete partitions)
- Added tests for 4 concurrent spark datasource writers (multi-writer tests).
- Fixed readme w/ sample commands for multi-writer.

docker/demo/config/test-suite/insert-overwrite.yaml

@@ -17,7 +17,6 @@ dag_name: simple-deltastreamer.yaml
 dag_rounds: 1
 dag_intermittent_delay_mins: 1
 dag_content:
-
   first_insert:
     config:
       record_size: 1000
@@ -91,4 +90,4 @@ dag_content:
       validate_hive: false
       delete_input_data: false
     type: ValidateDatasetNode
-    deps: third_upsert
+    deps: third_upsert