Revamp react-tokens logic

Describe the enhancement or change
Our token generation in the react-tokens package needs to be reworked as the logic we use to determine css var values doesn't match 1:1 with how that value will be determined in browser, this can lead to build breaking bugs with recursively defined values.

We've implemented a temporary fix for this, but it is still not optimal as differences in behavior could occur if a var is defined multiple times in a stylesheet. Ideally we should only parse the css within the root selector of the stylesheet.

Additionally, core currently has to add some variables to the root scope for the sole purpose of having the token created in react-tokens, ideally this will not be required in the future.

Jira Issue: PF-92

まず react-tokens パッケージと、その一時的なトークン生成の修正を見つけ、次に core がルートスコープに変数を追加する方法を調べます。パッケージの CSS 変数の解決をブラウザーの動作と比較します。特に、再帰的に定義された変数や複数回定義された変数を確認します。ルートスコープの解析がブラウザーの解決と一致し、core がトークンを作成するためだけに追加の変数を必要としなくなれば完了です。