feat: v3

[curlyfriesplease]

Version 3

This version:

• Moves to the highest available version of ESLint 8, 8.57.1. While v9 is available, many of our dependencies are not ready for it yet.
• Removes the unicorn plugin. Its ruleset is a bit too strict and contravenes a lot of our code, but not in ways that seem especially helpful to remediate.
• Adds the stylistic plugin, as a number of our rules have been deprecated by eslint-typescript and moved to that plugin instead.
• Adds an override to target TS files, see index.js
• SonarJS v3 is designed to align with ESLint v9's new config format, which uses a different export mechanism for configurations. Because of this, I have changed the SonarJS ruleset from 'recommended' to 'recommended-legacy'. This is specifically designed for ESLint v8 compatibility in eslint-plugin-sonarjs v3.0+ while maintaining the same rule configuration as the original recommended preset.
• Adds a large number of new tests. The majority have been AI generated and I have kept the ones I liked the look of.

ENG-3910

Testing

This has been tested as working on the following repos:
serverless-payments-bootstrap
serverless-fundraiser-signup
serverless-giftaid
serverless-prize-platform