chore: migrate internal linting to flat config

[MikeMcC399]

Issue

• ESLint v9 was released on Apr 5, 2024 and the announcement stated that "Flat config" is now the default.
• The configuration for internal linting is however still set up using .eslintrc.json which is considered legacy format moving into ESLint v9 where the standard configuration filename is in the form eslint.config.*js and the contents are in flat config form.
• Internal linting needs to use flat config as preparation to migrate to ESLint v9

This repo uses the following plugins for internal linting:

Plugin	version	recommended flat config option
eslint	8.57.0	pluginJs.configs.recommended
eslint-plugin-eslint-plugin	6.0.0	flat/recommended
eslint-plugin-mocha	10.4.3	mochaPlugin.configs.flat.recommended
eslint-plugin-n	17.2.1	flat/recommended-script

Related resolutions

• PR refactor: convert config .eslintrc.json to .js #199 provided a first step in migrating the ESLint config file towards a format used in the latest version of ESLint (v9).

Change

1. Install latest plugin versions
2. Install @eslint/js and @eslint/eslintrc
3. Replace the config file .eslintrc.js using eslint.config.mjs according to the documentation ESLint 8.x configuration files (new) and the documentation of each plugin.

References

Configuration Migration Guide

ESLint 8.x

• ESLint 8.x configuration files
• ESLint 8.x configuration files (new)

ESLint 9.x

• ESLint 9.x configuration files
• ESLint 9.x configuration files (deprecated)

Verification

Ubuntu 22.04.4 LTS, Node.js v20.12.2 LTS

npm ci
npm run lint

[cypress-app-bot]

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[jennifer-shehane]

Great!

[cypress-app-bot]

🎉 This PR is included in version 3.2.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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