[HDRP] Backport various PRs

[sebastienlagarde]

Purpose of this PR

Improve Path tracing docs https://github.com/Unity-Technologies/Graphics/pull/6494[](https://github.com/Vic-Cooper)[](https://github.com/sebastienlagarde)

[HDRP] Improves robustness of detail normal mapping when scale = 0 (a…

Add pragma renderer only for planar reflection preview shader (https://github.com/Unity-Technologies/Graphics/pull/7058[)](https://github.com/Unity-Technologies/Graphics/pull/7232/commits/789bf7be61afd883f0b1f9b23df0d445be198b8b)[](https://github.com/sebastienlagarde)

Fix wrong class name in the CustomPassUtils doc (https://github.com/Unity-Technologies/Graphics/pull/7063[)](https://github.com/Unity-Technologies/Graphics/pull/7232/commits/88fdf7cabc7f4beb667e0acb26c9fe4a46f22dbf)[](https://github.com/alelievr)[](https://github.com/sebastienlagarde)

Fix null check reference in CollectLightsForRayTracing (Fix 1398381) https://github.com/Unity-Technologies/Graphics/pull/7065[](https://github.com/sebastienlagarde)

Fixed camera motion vector pass reading last frame depth texture https://github.com/Unity-Technologies/Graphics/pull/7111[](https://github.com/JulienIgnace-Unity)[](https://github.com/sebastienlagarde)

Update Custom-Pass-Injection-Points.md (https://github.com/Unity-Technologies/Graphics/pull/7116[)](https://github.com/Unity-Technologies/Graphics/pull/7232/commits/2c5c7197433f53449a960236ae418c99cd7610c3)[](https://github.com/alelievr)[](https://github.com/sebastienlagarde)

Update Custom-Pass-Injection-Points.md (https://github.com/Unity-Technologies/Graphics/pull/7116[)](https://github.com/Unity-Technologies/Graphics/pull/7232/commits/c61bbca79148bd7998ee224e7a4f5420c3d2dff0)[](https://github.com/alelievr)[](https://github.com/sebastienlagarde)

Fix lunix compil issues (https://github.com/Unity-Technologies/Graphics/pull/7143[)](https://github.com/Unity-Technologies/Graphics/pull/7232/commits/eee5ef0aa633e50835901e5ce3848196789a4fe6)[](https://github.com/sebastienlagarde)

note bolding (https://github.com/Unity-Technologies/Graphics/pull/7161[)](https://github.com/Unity-Technologies/Graphics/pull/7232/commits/3aed00bd4da4bddae098f4a66385109674646a9f)[](https://github.com/emilybrown1)[](https://github.com/sebastienlagarde)[](https://github.com/Unity-Technologies/Graphics/tree/3aed00bd4da4bddae098f4a66385109674646a9f)

updated screenshots (https://github.com/Unity-Technologies/Graphics/pull/7164[)](https://github.com/Unity-Technologies/Graphics/pull/7232/commits/dfe769620e6388709a7f1911864b40136db855a5)[](https://github.com/emilybrown1)

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[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)

HDRP
/jobDefinition/.yamato%2Fall-hdrp.yml%23PR_HDRP_2021.2
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/jobDefinition/.yamato%2Fall-lightmapping.yml%23PR_Lightmapping_2021.2

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