Related to #

Proposed Changes

• Remove all issues related non instantiated definition. https://github.com/Automattic/wp-calypso/pull/94682/files#diff-ced52ec24ed2cc9e31a92a4d7d40e71b1062061fe0abccc5b0c082418b372731L62
• Remove field name conflicts with the backend expectations. It was causing overcomplicated mappings between both definitions. (code)
• Fix multiple rerenders issues caused by sequencias setErrors calls. (code)
• Move error handling to a separate hook

Testing Instructions

Base:

• Access any flow using the credential step (E.g site-migration/site-migration-credentials?from=[FROM]&siteSlug=[WP_COM_SITESLUG]&siteId=[WPCOM_SITE_ID]
• Follow the above scenarios

Scenario 1: (Credentials - Required Fields)

• Click on Continue without fill any field
• Check if you can see errors on the required fields (User and password)

Scenario 2: (Credentials - Create)

• Fill all fields with correct values
• Click on Continue
• Check if you are redirected to the next screen.

Scenario 3: (Backup file - Required Fields)

• Click on Continue without fill any field
• Check if you can see errors on the required fields (User and password)

Scenario 4: (Backup - Create)

• Fill all fields with correct values
• Click on Continue
• Check if you are redirected to the next screen

NOTE: These and more scenarios are tested via this test suite

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)?