Fix <WithRecord> render prop type

[slax57]

Problem

#8963 introduced a change to <WithRecord>, which allowed the render prop return a ReactNode instead of a ReactElement.
But since <WithRecord> currently returns the result of the render function without wrapping it in JSX first, we get the following TS error:

Solution

Wrap the result of the render function in a React Fragment.
Also, I removed the the RenderRecordFunction type because to me FunctionField and WithRecord do not share the same render function signature.

[slax57]

As @fzaninotto pointed out, WithRecord should actually support ReactNode. So I changed the component to allow for this useage.
I also edited the PR description accordingly.