fix: default create data to an empty object (#5707)
[TML-1034](https://linear.app/prisma-company/issue/TML-1034/create-method-has-weird-inconsistencies-and-correctness-issues-in)
We currently allow omitting the data field if none of the properties are
required, but that prevents the defaults from being evaluated. This PR
changes the query document to check for top-level defaults and the
`create_one` mutation to default the `data` object to an empty object.
