Fix on(Long)PressChange events in experimental press event API

[necolas]

Make sure that onPressChange is only called if longPressCancelsPress is false.
And make sure that onLongPressChange is called when a long press ends.

[trueadm]

LGTM minus the typo.

[sizebot]

Details of bundled changes.

Comparing: 700f17b...0c161b8

react-events

File	Filesize Diff	Gzip Diff	Prev Size	Current Size	Prev Gzip	Current Gzip	ENV
react-events.development.js	0.0%	+0.2%	1.16 KB	1.16 KB	617 B	618 B	UMD_DEV
react-events.production.min.js	0.0%	🔺+0.2%	682 B	682 B	430 B	431 B	UMD_PROD
react-events.development.js	0.0%	+0.4%	996 B	996 B	554 B	556 B	NODE_DEV
react-events-press.development.js	+3.3%	+1.2%	9.53 KB	9.85 KB	2.4 KB	2.43 KB	UMD_DEV
react-events-press.production.min.js	🔺+4.4%	🔺+1.1%	3.93 KB	4.11 KB	1.39 KB	1.4 KB	UMD_PROD
react-events-press.development.js	+3.4%	+1.2%	9.36 KB	9.68 KB	2.36 KB	2.39 KB	NODE_DEV
react-events-press.production.min.js	🔺+4.6%	🔺+1.5%	3.77 KB	3.95 KB	1.34 KB	1.36 KB	NODE_PROD
ReactEventsPress-dev.js	+3.6%	+1.6%	9.5 KB	9.84 KB	2.37 KB	2.41 KB	FB_WWW_DEV
ReactEventsPress-prod.js	🔺+3.7%	🔺+1.5%	7.65 KB	7.93 KB	1.71 KB	1.74 KB	FB_WWW_PROD
react-events-hover.development.js	0.0%	+0.1%	4.73 KB	4.73 KB	1.32 KB	1.33 KB	UMD_DEV
react-events-hover.production.min.js	0.0%	🔺+0.1%	2.12 KB	2.12 KB	902 B	903 B	UMD_PROD
react-events-hover.development.js	0.0%	+0.1%	4.56 KB	4.56 KB	1.28 KB	1.28 KB	NODE_DEV
react-events-hover.production.min.js	0.0%	🔺+0.2%	1.95 KB	1.95 KB	844 B	846 B	NODE_PROD

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