chore: extract loading braintree libraries to util/braintree #533

Job	Run time
Check	54s
Unit test (Chrome)	1m 39s
Unit test (Firefox)	1m 28s
Integration test with react-recurly	55s
Unit test (Safari-Remote)	5m 26s
Unit test (Electron)	1m 40s
Unit test (Edge-Remote)	3m 13s
Unit test (iOS-16-Remote)	4m 54s
Unit test (iOS-15-Remote)	7m 6s
Unit test (Android-13-Remote)	2m 32s
Unit test (Android-12-Remote)	6m 22s
Unit test (Android-11-Remote)	7m 2s
End-to-end test (Chrome-Remote)	2m 18s
End-to-end test (Firefox-Remote)	2m 54s
End-to-end test (Safari-Remote)	4m 28s
End-to-end test (Edge-Remote)	3m 35s
End-to-end test (iOS-16-Remote)	5m 24s
End-to-end test (iOS-15-Remote)	5m 9s
End-to-end test (Android-13-Remote)	3m 4s
End-to-end test (Android-12-Remote)	5m 58s
End-to-end test (Android-11-Remote)	3m 8s
Publish artifacts	36s
Verify required checks	1s
	1h 19m 46s

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