refactor: move tokens to their component directories

[andrewseguin]

Moves tokens out of core/tokens and into their respective component directories.

Also uses a new token-utils.slot() function that replaces create-tokens-slot:

// Before:
.mat-comp {
  @include token-utils.create-token-slot(border-radius, container-shape);
}

// After:
.mat-comp {
  border-radius: token-utils.slot(container-shape);
}