Remove onboarding/step-container-v2-migration-flow feature flag and conditional code

[markbiek]

Part of #DOTCON-76

Proposed Changes

Now that the StepContainerV2 feature flag is enabled in all environments, we can remove the flags as well as the conditional code in each migration component.

Testing Instructions

You'll want to use the calypso.live url since some of the application password paths can't be accessed locally.

• Go to /setup/site-migration.
• Go through all paths of the flow. This means doing a DIFM migration and a DIY migration. You'll also want to make sure that the links to the import flow also work, though you don't have to actually do an import.
• Verify that all steps look correct and function as expected.

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:build-147217

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-147217&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-147217&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

• blaze-dashboard
• help-center
• notifications
• odyssey-stats
• wpcom-block-editor

To test WordPress.com changes, run install-plugin.sh $pluginSlug DOTCON-76/remove-container-v2-flag on your sandbox.

[matticbot]

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

App Entrypoints (~343 bytes removed 📉 [gzipped])

name                    parsed_size           gzip_size
entry-stepper               -4470 B  (-0.3%)     -367 B  (-0.1%)
entry-domains-landing        -820 B  (-0.1%)     -261 B  (-0.1%)
entry-dashboard-dotcom       -820 B  (-0.1%)     -261 B  (-0.1%)
entry-dashboard-a4a          -820 B  (-0.1%)     -261 B  (-0.1%)
entry-browsehappy            -820 B  (-0.4%)     -261 B  (-0.4%)
entry-subscriptions          -770 B  (-0.0%)     -255 B  (-0.0%)
entry-reauth-required        -770 B  (-0.0%)     -243 B  (-0.0%)
entry-main                   -770 B  (-0.0%)     -243 B  (-0.0%)
entry-login                  -770 B  (-0.0%)     -243 B  (-0.0%)

Common code that is always downloaded and parsed every time the app is loaded, no matter which route is used.

Sections (~14 bytes removed 📉 [gzipped])

name                        parsed_size           gzip_size
people                           -103 B  (-0.0%)      -42 B  (-0.0%)
site-setup-flow                   +50 B  (+0.0%)      +18 B  (+0.0%)
onboarding-flow                   +50 B  (+0.0%)      +18 B  (+0.0%)
new-hosted-site-flow              +50 B  (+0.0%)      +18 B  (+0.0%)
hundred-year-plan                 +50 B  (+0.0%)      +18 B  (+0.0%)
hundred-year-domain               +50 B  (+0.0%)      +18 B  (+0.0%)
connect-domain                    +50 B  (+0.0%)      +18 B  (+0.0%)
async-step-use-my-domain          +50 B  (+0.0%)      +28 B  (+0.0%)
async-step-unified-plans          +50 B  (+0.0%)      +18 B  (+0.0%)
async-step-unified-domains        +50 B  (+0.0%)      +18 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.

Async-loaded Components (~18 bytes added 📈 [gzipped])

name                                       parsed_size           gzip_size
async-load-automattic-help-center-stepper        +50 B  (+0.0%)      +18 B  (+0.0%)

React components that are loaded lazily, when a certain part of UI is displayed for the first time.

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.