[FSSDK-10989] refactor notification center using event emitter #919

Job	Run time
crossbrowser_and_umd_unit_tests	6h 0m 14s
lint	58s
unit_tests (16)	1m 50s
unit_tests (18)	1m 34s
unit_tests (20)	1m 24s
unit_tests (22)	1m 22s
fullstack_production_suite / test	6s
lint_markdown_files / lint	2m 53s
integration_tests / test	5s
Coveralls coverage	4s
	6h 10m 30s

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