[FSSDK-10989] refactor notification center using event emitter (#975) #933

Job	Run time
lint	1m 3s
crossbrowser_and_umd_unit_tests	6h 0m 14s
unit_tests (16)	1m 37s
unit_tests (18)	1m 27s
unit_tests (20)	1m 29s
unit_tests (22)	1m 23s
fullstack_production_suite / test	8s
integration_tests / test	4s
lint_markdown_files / lint	1m 1s
Coveralls coverage	3s
	6h 8m 29s

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