[FSSDK-10642] Refactor batch event processor #865

Job	Run time
crossbrowser_and_umd_unit_tests	6h 0m 14s
lint	1m 4s
unit_tests (16)	1m 5s
unit_tests (18)	1m 6s
unit_tests (20)	1m 2s
unit_tests (22)	1m 5s
fullstack_production_suite / test	6s
integration_tests / test	7s
lint_markdown_files / lint	11m 0s
Coveralls coverage	0s
	6h 16m 49s

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