Store Picker: Add tracking for list editing

[itsmeichigo]

Part of #14658

Description

This PR adds tracking for the store picker update project:

Event	Trigger	Properties
*_site_picker_edit_button_shown	When the Edit button is available on the site picker.
*_site_picker_edit_button_tapped	When the user taps the Edit button on the top right.
*_site_picker_list_save_button_tapped	When the user taps the Save button on the edit store list screen	hidden_site_count
*_site_picker_list_saving_success	When saving is successful
*_site_picker_list_saving_failure	When saving faills	Error details

Steps to reproduce

• Build and run the app on a physical device.
• Log in to an account connected to more than one store.
• Navigate to Menu > Store Picker.
• Confirm that site_picker_edit_button_shown is tracked only once.
• Select the Edit button, confirm that site_picker_edit_button_tapped is tracked.
• De-select one or more stores in the list and tap Save. Confirm that site_picker_list_save_button_tapped is tracked with the correct value for hidden_site_count.
• After the saving succeeds, confirm that site_picker_list_saving_success is tracked.
• Disconnect the internet connection on the device and select Edit > update the selection > Save again.
• Confirm that site_picker_list_saving_failure is tracked with error details.

Testing information

Tested on iPhone 16 Pro iOS 18.1 and confirmed that tracking work as expected.

Screenshots

N/A

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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.

[dangermattic]

	1 Message
📖	This PR contains changes to Tracks-related logic. Please ensure (author and reviewer) the following are completed: The tracks events must be validated in the Tracks system. Verify the internal Tracks spreadsheet has also been updated. Please consider registering any new events. The PR must be assigned the category: tracks label.

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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	pr14762-ca41060
	Version	21.2
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	ca41060
	App Center Build	WooCommerce - Prototype Builds #12287

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