Provide access to reflection probe data in shader language

[bertodelrio256]

I understand in godot 4 that lights, decals, and reflection probes are all clustered. In the godot shader language, you can override the light function by using void light() {}. for custom shading the default behavior of probes has been insuffient for customization. for example, say i dont want color from the probe on metals, or i want a specific fresnel curve or i want an intensity brighter then 1.0. it would be immensly useful to have something like:

void reflections()
{
     ALBEDO *= PROBECOLOR.rgb * vec3(2.0) * skycolor.rgb;
}

[Calinou]

or i want an intensity brighter then 1.0.

See #7654, which has a pull request implementing it. You can also work around this by setting the ReflectionProbe's intensity property in a script, which bypasses the inspector hint's limits.