Experiment using ESLint FlatCompat to move to flat config

[romaricpascal]

What

Try using ESLint's FlatCompat class and other compatibility helpers to move our configuration to the new flat format and see if it'd allow npm update or Dependabot to run without errors.

Most of our plugins are compatible with the new format, but standard and eslint-plugin-import will need some workaround. This workaround for eslint-plugin-import may come handy to set them up.

Why

ESLint is making flat format the default for its configuration. However, not all plugins are ready for it, so we've had to disable dependabot for ESLint and its plugins, as it was timing out because of version incompatibilities.

ESLint is providing some utilities to make older plugins compatible with their new configuration format, so the hopes are that by using them, we can migrate to this new format and get updates for ESLint and its plugins.

Who needs to work on this

Developers

Who needs to review this

Developers

Done when

• We've tried migrating to a flat configuration using ESLint's compatibility helpers
• We've checked the impact on updating eslint related packages
• We've discussed the complexity of the workarounds we'd have to maintain
• If updates work OK again, we've re-enabled updates for ESLint and its plugins in Dependabot