fix: initialise nextjs webpack before importing devserver

[djsilcock]

• Closes [7.0.1] Component testing not working with Next.js and future.webpack5 configuration #15864

User facing changelog

Fixed integration with nextjs for component test runner

Additional details

NextJs provides its own webpack bundle, rather than listing it as a [peer] dependency. This leads to two separate instances, and potentially two separate versions, of webpack being in use simultaneously.
The NextJs config adds a require hook such that require('webpack') returns the bundled NextJs version appropriate to the {future:webpack5} setting in config.next.js - but as the @cypress/webpack-devserver package requires webpack, this only works if that package is required after the next config file has run

How has the user experience changed?

cypress open-ct now progresses to show test runner when next config is used as per the example in the repository

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