Enable virtualization for the block list on iOS

[fluiddot]

What problem does this address?

Following this comment, on iOS despite the use of FlatList component for rendering the block list, we are not benefitting from list virtualization due to nesting the FlatList under a scroll view. Lack of virtualization implies a high device resource consumption, especially in long posts.

What is your proposed solution?

Unify the ScrollView and FlatList rendering into a single FlatList component.

• Create an animated component for the FlatList.
• Move props passed from the ScrollView to the FlatList.
• Make necessary adjustments.

gutenberg/packages/components/src/mobile/keyboard-aware-flat-list/index.ios.js

Lines 146 to 158 in 5bf6aa0

	<AnimatedScrollView
	automaticallyAdjustContentInsets={ false }
	contentInset={ contentInset }
	keyboardShouldPersistTaps="handled"
	onContentSizeChange={ onContentSizeChange }
	onScroll={ scrollHandler }
	ref={ getRef }
	scrollEnabled={ scrollEnabled }
	scrollEventThrottle={ 16 }
	style={ style }
	>
	<FlatList { ...props } />
	</AnimatedScrollView>