feat: Initial steps for ESLint 9 upgrade (bot-provided)

[jdforrester]

[Commit made by Google Jules.]

This commit includes the initial changes for upgrading ESLint from v8 to v9.

Key changes made:

1. package.json Updates:

   • Updated peerDependencies.eslint to >=9.0.0.
   • Removed devDependencies.eslint-config-wikimedia due to current incompatibility with ESLint 9 and flat config.
   • Removed devDependencies.eslint-docgen due to likely incompatibility with ESLint 9's RuleTester changes and age.
   • Updated devDependencies.eslint-plugin-eslint-plugin from ^4.1.0 to ^6.4.0 for ESLint 9 compatibility.
   • Updated dependencies.eslint-plugin-vue from ^9.23.0 to ^10.1.0 for ESLint 9 compatibility.
   • Modified scripts.doc to remove eslint-docgen execution.

2. ESLint Configuration Migration:

   • Created eslint.config.js with a flat configuration structure.
   • Deleted the old .eslintrc.json (root) and tests/.eslintrc.json.
   • The new configuration currently omits wikimedia specific configs and relies on eslint-plugin-eslint-plugin and basic settings.

3. Custom Rule Updates (src/rules/):

   • Analyzed all custom rules for ESLint 9 compatibility.
   • Updated src/rules/valid-package-file-require.js: replaced context.getFilename() with context.filename.
   • Updated src/rules/vue-exports-component-directive.js: replaced context.getFilename() with context.filename.
   • Other rules (class-doc.js, msg-doc.js, no-extended-unicode-identifiers.js, no-nodelist-unsupported-methods.js, no-vue-dynamic-i18n.js) were checked and appear compatible with respect to schema, context usage (via utils or direct), and rule style.

Next Steps (as per original plan):

• Update rule tests in tests/rules/ for RuleTester changes and stricter checks.
• Run all tests (npm test) and address any failures or new linting errors.
• Review and update documentation if necessary.

I am providing this now as our current interaction is nearing its end. Further work is required to complete the ESLint 9 upgrade, particularly around updating and verifying the test suite.