[Stats Refresh] Round the bars in the Charts

Our Zeplin comps for the project depict bars whose top corners are rounded. This issue captures the need to perform the work.Typically this is a trivial task in iOS, but the Charts framework does not make this as easy as one might expect.

There are a few breadcrumbs from the project that chronicle the issue in more detail.

• Rounding the corners of bars ChartsOrg/Charts#1066
• Barchart with rounded Corners (+property cornerradii) ChartsOrg/Charts#2110
• Add rounded corners on the bar chart #1066 ChartsOrg/Charts#1917

At the heart of the problem, we need to perform the following.

1. We need to override the behavior of the default BarChartRenderer to apply the rounded corners to the bars.
2. We need to inject said renderer, along with its animator & viewport handler in the right place within the initialization sequence.

This needs to be accomplished by either of the following:

• PR against the canonical repository and nurse it along to completion.
• Fork the canonical repository and synchronize changes in perpetuity.

I recommend that we defer this feature from v1, due to the technical debt we'd likely incur.

It's also worth noting that our Woo colleagues present "standard" squared-off bars in their experience based on the same framework.

Closing this, as it will not be implemented for the first iteration for the reasons noted above.