[Fogbugz 1358506] Fixing shader graph codegen of preview shader hybrid v2, using hybrid…

[kecho]

Purpose of this PR

Fixed compilation problems on preview shader when using hybrid renderer v2 and property desc override Hybrid Per Instance.

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Testing status

Tested by following repro steps from fogbugz:

https://fogbugz.unity3d.com/f/cases/1358506/

[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://yamato.cds.internal.unity3d.com/jobs/902-Graphics
Search for your PR branch using the sidebar on the left, then add the following segment(s) to the end of the URL (you may need multiple tabs depending on how many packages you change)

Shader Graph
/.yamato%252Fall-shadergraph.yml%2523PR_ShaderGraph_2021.2
Depending on your PR, you may also want
/.yamato%252Fall-shadergraph_builtin_foundation.yml%2523PR_ShaderGraph_BuiltIn_Foundation_2021.2
/.yamato%252Fall-shadergraph_builtin_lighting.yml%2523PR_ShaderGraph_BuiltIn_Lighting_2021.2

Depending on the scope of your PR, you may need to run more jobs than what has been suggested. Please speak to your lead or a Graphics SDET (#devs-graphics-automation) if you are unsure.

[iM0ve]

Small change, testing the repro case should be enough

[cdxntchou]

Looks good!