[Shipping Lines] Add Shipping Method Selector view

[rachelmcr]

Part of: #12578

Why

Adds a new view to select a shipping method from a list of available shipping methods. For now, the view displays a static list of methods; this will be updated later to display the available shipping methods from the store.

How

Adds a new view with a list of selectable items populated (for now) by a static list of methods.

Notes:

• This doesn't use the SwiftUI List component because the SelectableItemRow has styling that doesn't work well in it. It might be worth eventually adjusting our reusable rows to work inside a List, since that does a lot of the formatting for us, but the various styles built into SelectableItemRow would take more significant work to style inside a list.
• I also chose not to use SingleSelectionList because its background and toolbar button don't match the designs for this view.

Testing instructions

This view is not yet used in the app.

Screenshots

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• [x] 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 in WooCommerce iOS by scanning the QR code below to install the corresponding build.

	App Name	WooCommerce iOS
	Build Number	pr12614-f3ec760
	Version	18.4
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	f3ec760457e15d74b750b901c52798d7412e61aa
	App Center Build	WooCommerce - Prototype Builds #8899

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