Stepper: Fix improper import in stepper for Sensei ErrorIcon

[sirbrillig]

Proposed Changes

The sensei-step-error components in the stepper reach into the private implementation details of the @automattic/composite-checkout package to use a component that's not part of the package API. That is fragile and will probably break in the future. This bug was added in #71406

In this PR we refactor that component to duplicate the component that was imported instead.

Testing Instructions

None should be needed.

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-79413

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-79413&env=jetpack

[matticbot]

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

Sections (~697 bytes removed 📉 [gzipped])

name            parsed_size           gzip_size
sensei-flow          -987 B  (-0.2%)     -376 B  (-0.3%)
site-purchases       -390 B  (-0.0%)     -161 B  (-0.0%)
purchases            -390 B  (-0.0%)     -161 B  (-0.0%)
checkout             -390 B  (-0.0%)     -160 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 (~160 bytes removed 📉 [gzipped])

name                                             parsed_size           gzip_size
async-load-calypso-my-sites-checkout-modal            -390 B  (-0.0%)     -160 B  (-0.0%)
async-load-calypso-blocks-editor-checkout-modal       -390 B  (-0.0%)     -160 B  (-0.1%)

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.