feat!: Use spacing tokens in Grid component

[VincentSmedinga]

This makes the Grid component use the new Space tokens, which were, in their turn, based on the Grid gap token.

• Uses Sass to generate classes for gap and padding. I intended to use shorter, local variable names, but prefixing with amsterdam is required.
• Introduces a .amsterdam-grid--gap--medium class that wasn’t previously there as the base component includes the medium gap class.
• The compact grid gap token is no longer needed; it now uses the token from compact mode if it’s loaded. The padding one is because its value is different.
• Replaces ‘white space’ with ‘gap’ in the docs; it is more specific and matches nicely with the prop name.

The change is breaking because:

1. the amsterdam-grid-gap token is now amsterdam-grid-gap-md
2. the large vertical padding of the grid is now 1.5 (instead of 2) times as wide as the regular gap width to match the space token naming