Upgrade to ESLint v9

[JstnMcBrd]

I have to wait until all dependencies have support for ESLint v9 before I can upgrade.

Flat config support is also nice, but not a requirement.

PR	Dependency	v9	Flat config	Links	Notes
#33	eslint-plugin-react-hooks	✅	❌	5.0.0 facebook/react#28313
	@stylistic/eslint-plugin	✅	✅	v2.4.0
	@types/eslint	✅	✅	9.6.0	Unnecessary - ESLint bundles their own type definitions now
	@types/eslint__js	❌	✅	DefinitelyTyped/DefinitelyTyped#69288	Might be compatible, but not updated to v9
#18	typescript-eslint	✅	✅	8.0.0
#12	eslint-plugin-react	⚠️	✅	7.35.0	Still relies on @types/eslint v7. Possibly switch to @eslint-react/eslint-plugin
#12	vscode-eslint	✅	✅	3.0.10

Some packages might work with ESLint Compat Utilities.

Updating to eslint v9 will also resolve some package deprecation warnings.

See eslint's master tracker: eslint/eslint#18391