raise avro version to 1.12.1 and aggregate property usage #1405

Job	Run time
Checkstyle	2m 30s
Build	58s
Spotless	2m 21s
Unit Tests	2m 1s
Dataflow Templates Integration Smoke Tests	1m 38s
Dataflow Templates Integration Tests	38m 19s
Dataflow Templates Load Tests	-1s
	47m 46s

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