Fix conflict between parent validation and function validation

[rpaul-stripe]

Due to splatting ...config after populating the validation property in validator.ts, the parents array would be overwritten whenever the user had a validation property in their top-level config — notably, when function validation is enabled. This PR fixes that issue and makes parent validation work as expected when function validation is turned on. It also adds a test case to explicitly check that this works.

The PR also adds support for setting render: false on a slot. Previously, the render attribute for a slot could only be used to change the prop name where the slot appears in the render tree. But there are cases where it's desirable to not have the slot render and be able to manually determine how to handle it in a transform function. I made a one-line change to make render: false work, consistent with how the render property works on regular tag attributes. I also added a marktest case for it.

Also increments the version number in package.json so that I can push a new release after these fixes land.