[DSIP-61][Master] Refactor thread pool and state event orchestration… #1

Job	Run time
Backend-Path-Filter	10s
Backend-Build (8)	15m 4s
Backend-Build (11)	16m 30s
schema-check (mysql, 3.1.9)	2m 40s
cluster-test-mysql-with-zookeeper-registry	2m 51s
schema-check (mysql, 3.2.0)	3m 43s
cluster-test-mysql-with-mysql-registry	4m 47s
schema-check (postgresql, 3.1.9)	2m 36s
cluster-test-postgresql-zookeeper-registry	2m 45s
schema-check (postgresql, 3.2.0)	2m 41s
cluster-test-postgresql-with-postgresql-registry	3m 2s
Build	1s
	56m 50s

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