Migrate away from backstop for visual regression testing

[JayPanoz]

I'm submitting a chore.

Short description of the issue/suggestion:

To put it simply, BackstopJS officially provides support up to Node v.20.x.x, the amount of issues in the repository is growing as well, and at some point I’m expecting automated tests will simply fail because of an issue between BackstopJS and Puppeteer.

Steps to reproduce the issue/enhancement:

Try to install while using Node v22 with the repo and you’ll get:

npm warn EBADENGINE Unsupported engine {
npm warn EBADENGINE   package: 'backstopjs@6.3.23',
npm warn EBADENGINE   required: { node: '>=16.0.0 <=20.x.x', npm: '>=8.0.0' },
npm warn EBADENGINE   current: { node: 'v22.12.0', npm: '10.9.0' }
npm warn EBADENGINE }

What is the expected behaviour?

We shouldn’t have to rely on an older version of Node.

What is the current behaviour?

The version is explicitly set through .nvmrc

What is the motivation / use case for changing the behaviour?

Long-term maintenance and support

Do you know which CSS modules (stylesheets) are impacted?

None, the automated tests are.