[FSSDK-10989] refactor notification center using event emitter #932

Job	Run time
lint	58s
unit_tests (16)	1m 38s
crossbrowser_and_umd_unit_tests	6h 0m 13s
unit_tests (18)	1m 32s
unit_tests (20)	1m 28s
unit_tests (22)	1m 25s
fullstack_production_suite / test	6s
integration_tests / test	4s
lint_markdown_files / lint	1m 9s
Coveralls coverage	2s
	6h 8m 35s

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