[Invoices] Invoices Are Confusing To Read

### Problem Statement

Invoices are confusing to read and become more confusing with each new SKU.

There are 3 core confusions:
- Parent/Child Relationship of charges
- The period for which the charge applies
- How tax is being applied (and tax refunds)

### Solution Brainstorm

Here is a real invoice for a customer:

I would recommend the following visual enhancements to address the 3 core confusions above:

**Note**: Breaking out VAT and subtotal amounts in the refund table row is not possible at this time as we do not have the mechanism to refund VAT and non-VAT charges.

Customers often want VAT and subtotal refunds separate as often-times we need to refund VAT when Billing Details are not configured correctly.

### Product Area

Settings - Subscription

No files, tests, or code entry points are named. Start by reviewing the Settings - Subscription invoice view and the two referenced screenshots, then clarify the intended handling of charge relationships, billing periods, taxes, and refunds. Done should mean the invoice is easier to read across these cases, with the refund limitation preserved.

Written by the indexing model from the issue text.