[core] Start simplifying styling API

[oliviertassinari]

First step toward #7636.

• Move the name option from createStyleSheet to withStyles.
• Move the option argument from createStyleSheet to withStyles.

Now, we should be able to hide createStyleSheet quite easily.

[patrickml]

@oliviertassinari with createStyleSheets removed how should we access the theme data?

For example I am currently doing things like this

export default createStyleSheet(theme => ({
  container: {
    borderBottom: `solid 1px ${theme.palette.common.faintBlack}`,
    display: 'flex',
    justifyContent: 'space-between',
    alignContent: 'center',
  }
}));

[oliviertassinari]

Have a look at the diff of #7740.

[molszanski]

Looked through the diff. Still don't get how to use the theme now in an elegant way. Tips appreciated :)

[oliviertassinari]

-export default createStyleSheet(theme => ({
+export default theme => ({
  container: {
    borderBottom: `solid 1px ${theme.palette.common.faintBlack}`,
    display: 'flex',
    justifyContent: 'space-between',
    alignContent: 'center',
  }
-}));
+});

[molszanski]

Much appreciated