[core] Remove withStyles from @material-ui/core

[mnajdova]

BREAKING CHANGE

The withStyles JSS utility is no longer exported from @material-ui/core/styles. You can use @material-ui/styles/withStyles instead. Make sure to add a ThemeProvider at the root of your application, as the defaultTheme is no longer available. If you are using this utility together with @material-ui/core, you should use the ThemeProvider component from @material-ui/core/styles instead.

-import { withStyles } from '@material-ui/core/styles';
+import { withStyles } from '@material-ui/styles';
+import { createTheme, ThemeProvider } from '@material-ui/core/styles';

+const defaultTheme = createTheme();
 const MyComponent = withStyles((props) => {
   const { classes, className, ...other } = props;
   return <div className={clsx(className, classes.root)} {...other} />
 })(({ theme }) => ({ root: { background: theme.palette.primary.main }}));

 function App() {
-  return <MyComponent />;
+  return <ThemeProvider theme={defaultTheme}><MyComponent /></ThemeProvider>;
 }

---

This was the last dependency on @material-ui/styles, we can remove it now from @material-ui/core.

[mui-pr-bot]

Details of bundle changes (experimental)

@material-ui/core: parsed: -8.08% 😍, gzip: -8.51% 😍
@material-ui/lab: parsed: -10.02% 😍, gzip: -10.56% 😍

Generated by 🚫 dangerJS against cdfcd7c

[mnajdova]

Looks like failing codemods is the last issue we need to solve - https://app.circleci.com/pipelines/github/mui-org/material-ui/42518/workflows/a47a4fe4-83ea-4651-9aa3-05427294135f/jobs/254836

@oliviertassinari @mbrookes what is the expected thing here?