chore: update @automattic/eslint-plugin-wpvip and migrate to ESLint 9

[sjinks]

Description

This pull request refactors the ESLint configuration to use the new flat config format, updates related dependencies, and cleans up various code and test files. The most significant changes include the migration from .eslintrc.js to eslint.config.js, updates to the ESLint plugin and Prettier dependencies, and removal of legacy ESLint ignore patterns. Additionally, minor code cleanups and improvements have been made throughout the codebase.

ESLint configuration migration and dependency updates:

• Migrated from .eslintrc.js to the new flat config format in eslint.config.js, updating how rules and ignores are set up for the project. ([1], [2])
• Updated @automattic/eslint-plugin-wpvip to point to the latest GitHub version and upgraded prettier to version 3.x in package.json. ([1], [2])
• Removed legacy ESLint ignore patterns from .eslintignore in favor of the new config format. (1)

Code and test file improvements:

• Removed or updated unnecessary ESLint disable comments and improved type annotations in test and source files for clarity and maintainability. ([1], [2], [3], [4], [5])
• Replaced deprecated or less accurate ESLint directive comments with up-to-date ones (e.g., switching from @typescript-eslint/no-var-requires to @typescript-eslint/no-require-imports). ([1], [2])

Minor code cleanups:

• Simplified constructor formatting and removed redundant type constituents and parameters in several files for better readability and stricter typing. ([1], [2], [3])
• Removed unnecessary comments and improved error handling and messaging in various utility and command files. ([1], [2], [3], [4], [5], [6], [7])

These changes modernize the project's linting setup, improve code quality, and lay the groundwork for easier future maintenance.

⚠️ After Automattic/eslint-config-wpvip#216 gets merged and we release a new version of automattic/eslint-config-wpvip, update package.json and set the correct version for automattic/eslint-config-wpvip.

Changelog Description

Changed

• Maintenance: update ESLint configuration and fix issues.

Pull request checklist

• Update SETUP.md with any new environmental variables.
• Update the documentation.
• Manually test the relevant changes.
• Follow the pull request checklist
• Add/update automated tests as needed.

New release checklist

• Automated tests pass.
• The Preparing for release checklist is completed.

Steps to Test

There are no functional changes. CI must pass.

[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

OpenSSF Scorecard

Package	Version	Score	Details
npm/@automattic/eslint-plugin-wpvip	github:automattic/eslint-config-wpvip#500ef87da9bc04b72469291c68525bf7a99df238	🟢 4.6	Details Check Score Reason Code-Review 🟢 10 all changesets reviewed Binary-Artifacts 🟢 10 no binaries found in the repo Token-Permissions ⚠️ 0 detected GitHub workflow tokens with excessive permissions Maintained ⚠️ 0 0 commit(s) and 0 issue activity found in the last 90 days -- score normalized to 0 Packaging ⚠️ -1 packaging workflow not detected Pinned-Dependencies ⚠️ 0 dependency not pinned by hash detected -- score normalized to 0 Dangerous-Workflow 🟢 10 no dangerous workflow patterns detected CII-Best-Practices ⚠️ 0 no effort to earn an OpenSSF best practices badge detected Fuzzing ⚠️ 0 project is not fuzzed License 🟢 10 license file detected Signed-Releases ⚠️ -1 no releases found Branch-Protection ⚠️ -1 internal error: error during branchesHandler.setup: internal error: some github tokens can't read classic branch protection rules: https://github.com/ossf/scorecard-action/blob/main/docs/authentication/fine-grained-auth-token.md Security-Policy ⚠️ 0 security policy file not detected SAST ⚠️ 0 SAST tool is not run on all commits -- score normalized to 0 Vulnerabilities 🟢 8 2 existing vulnerabilities detected
npm/prettier	npm:[email protected]	🟢 7	Details Check Score Reason Code-Review ⚠️ 2 Found 6/22 approved changesets -- score normalized to 2 Maintained 🟢 10 30 commit(s) and 17 issue activity found in the last 90 days -- score normalized to 10 Packaging ⚠️ -1 packaging workflow not detected Security-Policy 🟢 10 security policy file detected CII-Best-Practices ⚠️ 0 no effort to earn an OpenSSF best practices badge detected Dangerous-Workflow 🟢 10 no dangerous workflow patterns detected License 🟢 10 license file detected Branch-Protection ⚠️ -1 internal error: error during branchesHandler.setup: internal error: some github tokens can't read classic branch protection rules: https://github.com/ossf/scorecard-action/blob/main/docs/authentication/fine-grained-auth-token.md Signed-Releases ⚠️ -1 no releases found Token-Permissions ⚠️ 0 detected GitHub workflow tokens with excessive permissions Binary-Artifacts 🟢 10 no binaries found in the repo Pinned-Dependencies 🟢 8 dependency not pinned by hash detected -- score normalized to 8 Fuzzing ⚠️ 0 project is not fuzzed SAST 🟢 10 SAST tool is run on all commits Vulnerabilities 🟢 10 0 existing vulnerabilities detected

Scanned Files

• package.json

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[sjinks]

Related: #2617