[IPP] Delete simple payments migration flow

[kidinov]

Closes: #13813

Description

The PR deletes all the code related to Migrating from the Simple Payments flow that starts from payments hub

Steps to reproduce

Testing information

• Try to find any code that was not deleted, unused and related to the Simple Payments migration flow
• Validate that visually all good in the payments hub

The tests that have been performed

Above

Images/gif

• I have considered if this change warrants release notes and have added them to RELEASE-NOTES.txt if necessary. Use the "[Internal]" label for non-user-facing changes.

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 big (tablet) and small (phone) in case of UI changes, and no regressions are added.

[dangermattic]

	2 Errors
🚫	Please ensure the PR has the category: tracks label.
🚫	This PR is tagged with status: do not merge label(s).

	1 Warning
⚠️	This PR is larger than 300 lines of changes. Please consider splitting it into smaller PRs for easier and faster reviews.

	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.

Generated by 🚫 Danger

[wpmobilebot]

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

	App Name	WooCommerce-Wear Android
	Platform	⌚️ Wear OS
	Flavor	Jalapeno
	Build Type	Debug
	Commit	3325c9e
	Direct Download	woocommerce-wear-prototype-build-pr13814-3325c9e.apk

[wpmobilebot]

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

	App Name	WooCommerce Android
	Platform	📱 Mobile
	Flavor	Jalapeno
	Build Type	Debug
	Commit	3325c9e
	Direct Download	woocommerce-prototype-build-pr13814-3325c9e.apk

[kidinov]

Do not merge, as there is no final decision yet

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