Hotfix: Add condition check for "paid" cell index value

[ealeksandrov]

Closes: #7112

Description

In OrderDetailsDataSource refunds logic is relying on directly accessing array by index. Since refunds list is sharing section with other cells (see let payment: Section), index is calculated by subtracting 1 for "Payment" and "Paid by Customer" cells.

The crash appeared because we added condition to hide "Paid by Customer" when there are no payments yet.
Because index constants are static and not directly connected with section logic - we still subtract "-2" when there is only 1 extra cell in a section.

Fix

Static index replaced by a func (in the same Constants namespace) that requires boolean for its state to remind about the condition.
Maybe there is a better way without padding constants? I decided against logic refactor for now.

Testing

1. Prepare order without payments, but with refunds. Easy to do on the web, not sure about mobile.
2. Go to the Order tab, open order.
3. Confirm it doesn't crash.
4. Open "Refunded Products" list, confirm correct data.

Screenshots

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• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[peril-woocommerce]

	Warnings
⚠️	PR is not assigned to a milestone.

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[toupper]

LGTM! The code looks good and tests fine, thanks a lot @ealeksandrov 🚀

I decided against logic refactor for now.
I agree 👍