Remove Material UI import babel transformation

[codemonkey800]

Description

This removes the buggy babel transformation for Material UI imports. We originally used this so that we could improve build performance while using root imports like import { Accordion, Button } from '@material-ui/core'. However, this has proven to be very buggy (and occasionally blocking) for developers due to intermittent errors related to default exports:

/home/runner/work/example-plugin/example-plugin/napari-hub/frontend/node_modules/@material-ui/styles/esm/ServerStyleSheets/index.js:1
export { default } from './ServerStyleSheets';
^^^^^^

SyntaxError: Unexpected token 'export'
    at Object.compileFunction (node:vm:352:18)
    at wrapSafe (node:internal/modules/cjs/loader:1031:15)
    at Module._compile (node:internal/modules/cjs/loader:1065:27)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1153:10)
    at Module.load (node:internal/modules/cjs/loader:981:32)
    at Function.Module._load (node:internal/modules/cjs/loader:822:12)
    at Module.require (node:internal/modules/cjs/loader:1005:19)
    at require (node:internal/modules/cjs/helpers:102:18)
    at Object.4309 (/home/runner/work/example-plugin/example-plugin/napari-hub/frontend/.next/server/pages/_document.js:20:43)
    at __webpack_require__ (/home/runner/work/example-plugin/example-plugin/napari-hub/frontend/.next/server/webpack-runtime.js:25:42) {
  type: 'SyntaxError'
}

With no clear solution in sight, and with Next.js removing babel in the v12 release, this PR refactors the imports to import from the module directly instead of from the root import.

This also adds an eslint plugin that verifies that root imports aren't being used in the app, so using the following imports will now throw an eslint error:

import { Button } from '@material-ui/core';
import { Add } from '@material-ui/icons';
import { CSSProperties } from '@material-ui/styles';

Demo

[DragaDoncila]

Looks fine to me, love the eslint rule!