perf: investigate optimization for updateViews() in repeat

[prudepixie]

Following some investigation around repeat performance, we looked at a couple of scenarios:

1. push new element into array
2. updating existing section of array with new elements

updateViews() in RepeatBehavior class is triggered when array is updated (.splice() , .push()),
According to findings:
"In the way, it will try to apply splice on views, and try to reuse the removed views to bind with new data, insert them to new locations. It looks better than refreshAllViews since it only applies bindView to those updated items,
However, updateViews will always invoke insertBefore, even if it’s an in-place update, like array.splice(0, 1, array[0])."

Some possible points of investigation and benchmarks to write are:

• Make view.insertBefore() noop when an attempt to insert at the existing location is made
• Make the repeat skip inserting when the view already exists at the location

[prudepixie]

Refer to findings here: Repeat Benchmarks Report