[Shipping labels] Locally validate the address fields and display validation errors

[rachelmcr]

Closes: #14943
⚠️ Depends on #14949 ⚠️

Description

This adds the address validation behavior and UI to the Woo Shipping flow:

1. When a merchant opens the address form, we will immediately validate the address form and show any errors for invalid fields.
2. When a merchant types in any input fields, we will wait some seconds after the typing stops and perform a validation.
3. If the value of an input field is not valid, we will display an error.
4. When a merchant starts typing again on an input field with an error, we will clear the error and wait for the merchant to stop typing and validate the input as in step 2.
5. When we change focus from one input field to another, we will validate the value of the input field that lost the focus.

Changes

• We immediately validate all fields in the address when WooShippingEditAddressViewModel inits.
• We add a debounce before validating new values for WooShippingAddressField, and when cross-validating the name and shipping fields. This allows us to delay validation while a merchant is typing.
• We add a WooShippingAddressField.clearError() method and use it to clear any error when new text is being entered in an address text field.
• When observing the company and name fields, we immediately clear both fields when one changes and (after a delay) re-validate them.
• In the view, we add the UI to display the error message for a field. We also observe changes to the focused field and validate the previous field when it changes.

Testing information

1. Ensure the latest production version of WooCommerce Shipping (Version 1.3.2) 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 edit address sheet, confirm the address is validated as expected when the sheet opens.
8. Erase the text from a required field, wait a second, and confirm the expected validation error appears.
9. Start typing in the same field and confirm the validation error immediately disappears.
10. Erase the text from a required field, change the focus to a new field, and confirm the previous field is immediately validated.

Confirm that at each step the status label and button at the bottom of the sheet reflect the current validation status.

Screenshots

Simulator.Screen.Recording.-.iPhone.16.Pro.-.2025-01-22.at.20.34.52.mp4

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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.

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.

[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	pr14950-0f07e85
	Version	21.4
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	0f07e85
	App Center Build	WooCommerce - Prototype Builds #12665

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

[toupper]

LGTM! The validation delay looks great 🚢

[dangermattic]

	1 Warning
⚠️	This PR is assigned to the milestone 21.5. This milestone is due in less than 2 days. Please make sure to get it merged by then or assign it to a milestone with a later deadline.

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