chore: move to Eslint flat config

Make the big move to Eslint flat config format. The outcome of Eslint
still should be the same, but some things has changed:
- `eslint-plugin-github` is dropped, flat configs have been out for a
while and most eslint plugins support it, but for no reason and no
activity in sight this plugin is likely not going to support flat config
for a while and to avoid other plugins not being able to update (as they
are requiring flat configs) drop the github rules.
- Nested configs don't work properly and are unified into the root
eslint config, this unification did cause some conflicts and thats why
the `import-x` is in a seperate 'group' to exclude targeting Vue files.
- The `eslint-plugin-i` is deprecated and `esplint-plugin-import-x` is
its succesor which has better support for flat configs, the same rules
are still applied.

The majority of the flat config was generated by
`@eslint/migrate-config` tool.

tests/e2e/.eslintrc.yaml

@@ -1,24 +0,0 @@
-plugins:
-  - eslint-plugin-playwright
-
-extends:
-  - ../../.eslintrc.yaml
-  - plugin:playwright/recommended
-
-parserOptions:
-  sourceType: module
-  ecmaVersion: latest
-
-env:
-  browser: true
-
-rules:
-  playwright/no-conditional-in-test: [0]
-  playwright/no-conditional-expect: [0]
-  playwright/no-networkidle: [0]
-  playwright/no-skipped-test: [2, {allowConditional: true}]
-  playwright/prefer-comparison-matcher: [2]
-  playwright/prefer-equality-matcher: [2]
-  playwright/prefer-to-contain: [2]
-  playwright/prefer-to-have-length: [2]
-  playwright/require-to-throw-message: [2]