Revert "Oracle refactoring work" (#448) #873

Job	Run time
build (mysql-plugin)	48m 31s
build (mysql-plugin)	48m 31s
build (postgresql-plugin)	22m 48s
build (postgresql-plugin)	15m 57s
build (oracle-plugin)	1h 21m 13s
build (oracle-plugin)	1h 17m 8s
build (mssql-plugin)	49m 25s
build (mssql-plugin)	49m 25s
build (cloudsql-mysql-plugin)	43m 25s
build (cloudsql-mysql-plugin)	43m 25s
build (cloudsql-postgresql-plugin)	37m 50s
build (cloudsql-postgresql-plugin)	37m 50s
	9h 15m 28s

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