Fix reflections with smoothness debug mode on URP

[arttu-peltonen]

Purpose of this PR

Fixes 1374181. Currently the "Reflections with Smoothness" lighting debug mode on URP doesn't make sense. This PR fixes that. See screenshots for comparison.

To recap, the "Reflection" debug mode describes what the specular portion of lighting would look like using perfectly smooth mirror-like materials. The "Reflection with smoothness" debug mode does the same thing, but doesn't override smoothness to 1 and instead uses the smoothness value from each material.

Debug mode: None:

Debug mode: Reflection (before & after):

Debug mode: Reflection with smoothness (before):

Debug mode: Reflection with smoothness (after):

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Testing status

Tested debug mode manually in URP template.

[github-actions]

Hi! This comment will help you figure out which jobs to run before merging your PR. The suggestions are dynamic based on what files you have changed.
Link to Yamato: https://unity-ci.cds.internal.unity3d.com/project/902/
Search for your PR branch using the search bar at the top, then add the following segment(s) to the end of the URL (you may need multiple tabs depending on how many packages you change)

URP
/jobDefinition/.yamato%252Fall-urp.yml%2523PR_URP_trunk
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/jobDefinition/.yamato%252Fall-lightmapper.yml%2523PR_LightMapper_trunk

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[Jonasmortensen]

Looks good!

[arttu-peltonen]

Yamato is green, except for decals failure on URP_Terrain that was introduced in #5961.