Onboarding: Fix the browser back button redirects people to the plan step

[arthur791004]

Related to https://github.com/Automattic/dotcom-forge/issues/7232

Proposed Changes

• The issue is the new user survey step was dynamically excluded by the excludeSurveyStepIfInactive when the fulfilledStepCallback was triggered. However, we redirected people to the first step when they entered the flow, so the URL was recorded by the browser. Next, people got back to the new user survey step when they clicked the browser back button. The step was excluded so calypso redirected the user to the next step, that was the "Plan" step 💥
• As a result, this PR made a change to check whether the new user survey step is available, and then do the first redirection to resolve this issue.

Testing Instructions

1. Go to /sites
2. Click Add new site
3. Click anywhere on that page
4. Go back using the browser back button
5. Make sure it redirects you back to the /sites page

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)?

[matticbot]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-108085

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-108085&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-108085&env=a8c-for-agencies

[matticbot]

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

Sections (~15 bytes added 📈 [gzipped])

name    parsed_size           gzip_size
signup        +59 B  (+0.0%)      +15 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.

[matticbot]

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

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

• wpcom-block-editor

To test WordPress.com changes, run install-plugin.sh $pluginSlug fix/onboarding-browser-back on your sandbox.

[mmtr]

Works as described