Fix: Cycles film exposure maximum is too low

The previous value was incorrectly assuming this is 2^exposure, but it
is a simple multiplier.

Specifying large film exposure values is useful as it affects the raw data and
thus results in the same color values available in EXR, Viewer, and
Compositor, whereas using Color Management exposure is not reflected in EXR
exports, resulting in unusably low values. Using film exposure remedies that.

Pull Request: https://projects.blender.org/blender/blender/pulls/138850

intern/cycles/blender/addon/properties.py

@@ -850,7 +850,7 @@ class CyclesRenderSettings(bpy.types.PropertyGroup):
     film_exposure: FloatProperty(
         name="Exposure",
         description="Image brightness scale",
-        min=0.0, max=10.0,
+        min=0.0, soft_max=2**10, max=2**32,
         default=1.0,
     )
     film_transparent_glass: BoolProperty(