Refactor and add tests for Popovers #30939

Job	Run time
setup-selenium / setup_chromedriver	7s
build-client / build-client	9m 59s
Test (3.8, 0)	39m 31s
Test (3.8, 1)	48m 28s
Test (3.8, 2)	46m 4s
	2h 24m 9s

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