[system] Support using applyStyles inside template literals

[DiegoAndai]

Summary

This should be supported out of the box:

const theme = createTheme({});

const StyledButton = styled('button')`
  ${theme.applyStyles(
    'dark', `
      background: white;
    `
  )}
`;

But it's not because theme.applyStyles returns an object. The current workaround is to override applyStyles.

Motivation

Taken from #44488

Search keywords: applyStyles template literals