chore: Migrate to ESLint flat config in root directory

[lotmek]

Description

Continuing the work for #10897.
Flat configs already exist in ESLint v8.
I've followed the Configuration Migration Guide to enable ESLint flat config only at the root level

• Create a flat config file eslint.config.mjs at the root of the project
• Use the configuration migrator to start the migration
• Migrate all the plugins to the new format
• Handle shared configs at the root level
  • buildSharedConfig was implemented to add the configs to the related sub-packages
• Ignore new rules that were introduced (check TODO)

[peterp]

@lotmek This is awesome work, I'll make sure to get this prioritized this week.