Create pending sticker when loading the "how to migrate" step

[renatho]

Related to #95288

Proposed Changes

• Create the sticker when loading the "How to migrate" step.
• Extract hook to simplify step code.

Why are these changes being made?

• We want to register the migration-pending when the user is navigating through the migration flow. See more in p1728684758970459/1728480467.656839-slack-C07N53UNUQJ.

Testing Instructions

To check the status creation, you check the network tab of your browser filtering by /site-migration-status-sticker. To make sure the status was created, you can check it directly in your sandbox (p1729023356708799/1728480467.656839-slack-C07N53UNUQJ).

Test the following steps in /setup/migration and in the /setup/hosted-site-migration:

• Navigate to the "How to migrate" step.
• Check that it register the pending status.
• Click on the options, and make sure it continues registering the pending status for the "DIY" and "DIFM".

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the "[Status] String Freeze" label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
• For changes affecting Jetpack: Have we added the "[Status] Needs Privacy Updates" label if this pull request changes what data or activity we track or use (p4TIVU-aUh-p2)?

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-121942

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-121942&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-121942&env=a8c-for-agencies

[matticbot]

This PR modifies the release build for the following Calypso Apps:

For info about this notification, see here: PCYsg-OT6-p2

• notifications
• wpcom-block-editor

To test WordPress.com changes, run install-plugin.sh $pluginSlug add/migration-pending-status on your sandbox.

[matticbot]

This PR does not affect the size of JS and CSS bundles shipped to the user's browser.

Generated by performance advisor bot at iscalypsofastyet.com.