[Shipping labels] Make edit address form reusable for both origin and destination addresses

[rachelmcr]

Part of: #13781
⚠️ Depends on #14865 ⚠️

Description

This makes the address form in the Woo Shipping label flow reusable for editing both origin and destination addresses.

Changes in this PR:

• Adds an addressType property to track what type of address is being edited.
• Only shows the "Save as default" toggle for origin addresses. (And renames the saveAsDefault property to isDefault for clarity.)
• Adds a convenience initializer to the view model for editing origin addresses.

Testing information

There should be no visible changes to the current behavior:

1. Ensure the Woo Shipping extension is installed, activated, and set up on your store.
2. Create or open an order with at least one physical product and the processing status.
3. Tap "Create Shipping Label" in order details.
4. Open the "Shipment details" bottom sheet.
5. Tap the "Ship from" origin address.
6. Tap the edit (pencil) icon on one of the origin addresses.
7. In the address form, confirm you still see the "save as default" toggle at the bottom of the form.
8. Confirm all of the fields are pre-populated with the expected address details.

---

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

Reviewer (or Author, in the case of optional code reviews):

Please make sure these conditions are met before approving the PR, or request changes if the PR needs improvement:

• The PR is small and has a clear, single focus, or a valid explanation is provided in the description. If needed, please request to split it into smaller PRs.
• Ensure Adequate Unit Test Coverage: The changes are reasonably covered by unit tests or an explanation is provided in the PR description.
• Manual Testing: The author listed all the tests they ran, including smoke tests when needed (e.g., for refactorings). The reviewer confirmed that the PR works as expected on all devices (phone/tablet) and no regressions are added.

[dangermattic]

	1 Warning
⚠️	View files have been modified, but no screenshot or video is included in the pull request. Consider adding some for clarity.

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[wpmobilebot]

📲 You can test the changes from this Pull Request in WooCommerce iOS by scanning the QR code below to install the corresponding build.

	App Name	WooCommerce iOS
	Build Number	pr14866-babdfa1
	Version	21.4
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	babdfa1
	App Center Build	WooCommerce - Prototype Builds #12542

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.

[rachelmcr]

Checking on the build failure with the infra team: p1736878667017449-slack-CC7L49W13

[toupper]

Minor thing, can we make this property more meaningful? What is default here, the address? in that case, can we name it as isDefaultAddress?

[rachelmcr]

Yep, good point; updated both the property and the init parameter in babdfa1.

[toupper]

LGTM! 🚀 🚢