Site Migration: Remove automated-migration/collect-credentials feature flag and references to SOURCE_URL step

[gabrielcaires]

Proposed Changes

• Remove all references to automated-migration/collect-credentials from /setup/migration and /setup/site-migration (and hosted-site-migration as consequence)
• Remove all references to the old migration-source-url step, which only captured the user domain. Now, we can capture way more data with the credentials step.
• Delete the test cases the feature is off

Why are these changes being made?

• Code cleanup to improve maintenance

Testing Instructions

• Go to any of our migration flows (e.g./setup/hosted-site-migration)
• Choose DIFM
• Follow the steps and check if you can see the credentials setup

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 UI changes, have we tested the change in various languages (for example, ES, PT, FR, or DE)? The length of text and words vary significantly between languages.
• 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:commit-036325c629545ffd62b8f86399699a5fd89c4182

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:commit-036325c629545ffd62b8f86399699a5fd89c4182&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:commit-036325c629545ffd62b8f86399699a5fd89c4182&env=a8c-for-agencies

[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

Sections (~136 bytes removed 📉 [gzipped])

name                        parsed_size           gzip_size
site-migration-flow              -275 B  (-0.2%)      -44 B  (-0.2%)
hosted-site-migration-flow       -275 B  (-0.2%)      -44 B  (-0.2%)
migration-flow                   -201 B  (-0.2%)      -75 B  (-0.4%)
import-hosted-site-flow          -114 B  (-0.0%)      -17 B  (-0.0%)

Sections contain code specific for a given set of routes. Is downloaded and parsed only when a particular route is navigated to.

Legend

What is parsed and gzip size?

Parsed Size: Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory.
Gzip Size: Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.

[andres-blanco]

🚀