Use ESLint flat configurations

[dotNomad]

This work is on hold until:

• eslint-plugin-cypress upgrades to support the new flat config format:
  • Eliminate the need for an internal & public ESLint package cypress-io/cypress#24251
  • Upgrade to new ESLint Flat configuration files cypress-io/eslint-plugin-cypress#146

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ESLint v9.0.0 (which is currently in beta.1) will make the eslint.config.js configuration format the default and deprecate the current configuration method. In ESLint 10 our current configuration will no longer be supported.

Note that we cannot use ESLint v9 directly because the typescript-eslint/typescript-eslint#8211 just yet, but can use the configuration format since it is supported in v8 (as long as our extends support it too).

See #1030 for more comments about this as things were figured out.

References

• ESLint 9.0 migration doc

[dotNomad]

eslint-plugin-vue just added support for the flat config: vuejs/eslint-plugin-vue#1291