APP-2482: remove unnecessary ESLint and TypeScript rules

[mcous]

Overview

Disable some rules that have been giving us grief:

ESLint

• Turn off no-undef-init and unicorn/no-useless-undefined
• In tests, turn off @typescript-eslint/no-unsafe-assignment and sonarjs/no-duplicate-string
• In .svelte, turn off sonarjs/no-unused-collection because it crashes ESLint
• When using arrow functions, disable no-confusing-void-expression so we're not forced to use a bunch of braces in event handlers

TypeScript

• Turn off noPropertyAccessFromIndexSignature, because it's a purely stylistic concern, and it interacts poorly with with Svelte when components are accessed from Record objects
  • BREAKING CHANGE: this compiler option change will change linting behavior, which may cause previously passing code to start failing lint

[DTCurrie]

✅