Reorganise props handling in Field
Reorganise props handling in Field

Several small tweaks to the props handling:

* Use destructuring instead of `delete`
* Emphasize the `element` as a primary prop
* Document `textarea` as supported

matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk