feat: expose RemoteFormSubmitFunction type

[RazinShafayet2007]

Closes #15038

Exposes a public RemoteFormSubmitFunction type for remote form enhance callbacks, so users no longer need to derive the callback type manually from Parameters<typeof myForm.enhance>[0]. It reuses that exported type in RemoteForm['enhance'], regenerates the published declarations, and adds a type test covering both submit() and submit().updates(...) usage.

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Latest commit: 52e7d15

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