Add the interface to `userEvent.upload()` to simulate cancelling file select

Describe the feature you'd like:

I propose the interface to simulate cancelling file select.

DOM events (for example, a change event) on input elements with type="file" doesn't include .files when users cancel to select files.

events.target.files // undefined

However, there is not the interface to simulate this on userEvent.upload().

Suggested implementation:

For example,

// it accepts `undefined` and deletes event.target.files
userEvent.upload()

Describe alternatives you've considered:

Now I am simulating with fireEvent.change() like

const input = getTestById('file-input')
input.value=""
await fileEvent.change(input)

Teachability, Documentation, Adoption, Migration Strategy:

Nothing

I'm sorry in advance for my poor english.

If I can provide more information, please let me know.

Start by locating the userEvent.upload() entry point and reading how it currently handles file selection and cancellation. Review the surrounding tests and existing API behavior, then verify that the proposed cancellation call produces the expected file-input event state.