[Reliability] Add fallbacks for known Order decoding errors

[rachelmcr]

Closes: #9836, #7842

Description

This PR increases the app's resilience when Order fields have unexpected types:

• When a Order shipping line's tax ID is a String instead of an Int.
• When Order line item's SKU is a number (Int or Decimal) instead of a String.

It uses failsafe decoding to handle those alternative types, and adds a unit test for parsing alternative types in an Order. (These are known decoding errors that users have experienced.)

Testing instructions

We don't know the exact plugins that can cause this behavior, but you can test using a tool like Charles Proxy or Proxyman to intercept and modify the response:

1. Set a breakpoint in your tool of choice for requests to the /wc/v3/orders endpoint.
2. Build and run the app.
3. Open the Orders tab.
4. Modify the response so a shipping line tax ID is a string (e.g. "shipping_lines": [{ [...], "taxes": [{ "id": "1"}] }] or see the order-alternative-types.json mock for an example).
5. Modify the response so a line item SKU is a number (e.g. "line_items": [{ [...] "sku": 123 }]).
6. Execute the response and confirm the app loads the order list.

Screenshots

Before	After

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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.

[wpmobilebot]

You can test the changes from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr9844-4c849a5 on your iPhone

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