Do not extract candidates containing JS string interpolation pattern ${

[RobinMalfait]

This PR fixes an issue where often people run into issues where they try to use string interpolation and it doesn't work. Even worse, it could result in crashes because we will actually generate CSS. This fix only filters out candidates with a pattern like ${. If this occurs in a string position it is fine.

Another solution would be to add a pre processor for JS/TS (and all thousand file extension combinations) but the problem is that you can also write JS in HTML files so we would have to pre process HTML as well which would not be ideal.

Test plan

1. Added tests to prove this works in arbitrary values, arbitrary variables in both utilities and variants.
2. Existing tests pass.
3. Some screenshots with before / after situations:

Given this input:

let color = '#0088cc';
let opacity = 0.8;
let name = 'variable-name';
let classes = [
  // Arbitrary Properties
  `[color:${color}]`
  `[${property}:value]`,
  `[--img:url('https://example.com?q=${name}')]`, // WONT WORK BUT VALID CSS

  // Arbitrary Values
  `bg-[${color}]`,

  // Arbitrary Variables
  `bg-(--my-${color})`,
  `bg-(--my-color,${color})`,

  // Arbitrary Modifier
  `bg-red-500/[${opacity}]`,
  `bg-red-500/(--my-${name})`,
  `bg-red-500/(--my-opacity,${opacity})`,

  // Arbitrary Variant
  `data-[state=${name}]:flex`,
  `supports-(--my-${name}):flex`,
  `[@media(width>=${value})]:flex`,
];

This is the result:

Before	After

Fixes: #17054
Fixes: #15853

[philipp-spiess]

Nice one!

[philipp-spiess]

@RobinMalfait Here's another issue that is resolved by this I think: #15853