SetComponentsFunction does not allow multiple components

The `SetComponentsFunction` loot table function introduced in 1.21 has a private constructor for a `DataComponentPatch`, which can contain multiple data components.

However, the only public way to create this function is via the `setComponent` static method, which only accepts a single component.

This makes it impossible to use this function to generate more than one component on an item in a concise manner; thus it's possible to manually write a loot table JSON that's impossible to datagen.