[TIMOB-14290] (3_2_X)  iOS: ListView: scrollToItem lags with large lists

Backport of PR #5156

Fixes 
[TIMOB-14290](https://jira.appcelerator.org/browse/TIMOB-14290)
[TIMOB-15848](https://jira.appcelerator.org/browse/TIMOB-15848)