Stepper: Apply extended props to calypso_stepper_flow_start

[chriskmnds]

Part of addressing #94108

Proposed Changes

• Adds STEPPER_TRACKS_EVENT_FLOW_START
• Implements props extension for calypso_stepper_flow_start event
• Some general refactors to useFlowAnalytics. Also converted to useFlowStartTracking

DO NOT MERGE - depended on ongoing discussions in #94175 (similar/same problem)

Why are these changes being made?

• Allow flows to extend the default props tracked by Stepper for all the major/framework events

Testing Instructions

• test /setup/onboarding and /setup/newsletter
• ensure tracking of calypso_stepper_flow_start when walking through steps in Stepper works like before
• should fire once per flow

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-118124

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-118124&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-118124&env=a8c-for-agencies

[matticbot]

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

App Entrypoints (~238 bytes added 📈 [gzipped])

name                 parsed_size           gzip_size
entry-stepper             +868 B  (+0.0%)     +222 B  (+0.0%)
entry-subscriptions       +280 B  (+0.0%)      +48 B  (+0.0%)
entry-main                +280 B  (+0.0%)      +45 B  (+0.0%)
entry-login               +280 B  (+0.0%)      +45 B  (+0.0%)

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

Sections (~316 bytes removed 📉 [gzipped])

name                     parsed_size           gzip_size
jetpack-connect               -208 B  (-0.0%)      -38 B  (-0.0%)
domains                       -208 B  (-0.0%)      -49 B  (-0.0%)
themes                        -195 B  (-0.0%)      -47 B  (-0.0%)
signup                        -195 B  (-0.1%)      -57 B  (-0.1%)
posts-custom                  -195 B  (-0.0%)      -47 B  (-0.0%)
posts                         -195 B  (-0.0%)      -47 B  (-0.0%)
checkout                      -195 B  (-0.0%)      -54 B  (-0.0%)
accept-invite                 -195 B  (-0.1%)      -55 B  (-0.1%)
tailored-ecommerce-flow       +105 B  (+0.2%)      +31 B  (+0.5%)

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 (~228 bytes removed 📉 [gzipped])

name                                                         parsed_size           gzip_size
async-load-design-blocks                                          -208 B  (-0.0%)      -51 B  (-0.0%)
async-load-calypso-my-sites-site-settings-seo-settings-form       -208 B  (-0.1%)      -53 B  (-0.1%)
async-load-calypso-components-web-preview-component               -195 B  (-0.0%)      -71 B  (-0.1%)
async-load-calypso-blocks-editor-checkout-modal                   -195 B  (-0.0%)      -53 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.

[chriskmnds]

Similarly to #94229 (comment).
Closing this for now.