[FSSDK-10989] refactor notification center using event emitter #920

Job	Run time
crossbrowser_and_umd_unit_tests	6h 0m 13s
lint	59s
unit_tests (16)	1m 41s
unit_tests (18)	1m 32s
unit_tests (20)	1m 28s
unit_tests (22)	1m 31s
fullstack_production_suite / test	4s
integration_tests / test	4s
lint_markdown_files / lint	1m 7s
Coveralls coverage	4s
	6h 8m 43s

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