Split out test dependencies

As we discussed and put into OEP-67:

To keep installation and deployment of our MFEs as fast as possible, the “dependencies” field in package.json should reference only the packages needed to build the bundle of the MFE (this includes webpack via frontend-build, as well as any dependencies used in the actual MFE/React code). Any dependencies used only for testing, linting, formatting, or other development tasks should be put into “devDependencies” (e.g. Jest, eslint, TypeScript, @types/ packages, etc.).

However, this repo currently has almost all its dependencies, including the huge jest test runner ecosystem, in dependencies.

If this is just an oversight, things like jest, estlint, react-refresh, webpack-bundle-analyzer, etc. should be moved into devDependencies.

If this is because we want that tooling installed for use by consuming MFEs, I think those should be moved into a separate frontend-testing package, or even better, a frontend-testing sub-package within this same repository.