[7.x.x] Add SpeedTree8 shadergraph to HDRP and URP

[nerites]

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Purpose of this PR

Adding SpeedTree8 support (including material upgrader) to HDRP.
Added the SpeedTree8 shadergraph to URP as well, though the default is still the original SpeedTree8 shader pending wind support in the shadergraph.
Added a graphics test in HDRP for SpeedTree8. Also added SpeedTrees to the terrainlit and terrainbaselit test scenes.

TODO: Move SpeedTree8MaterialUpgrader from Core to Shadergraph package? -> Even invoking MaterialUpgrader using Core.Editor.MaterialUpgrader does not find the class from the shadergraph package, for some reason. Why?

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Testing status

Tested importing and material upgrading in HDRP. It works, except for an issue with embedded materials where when the Library is nuked, the materials don't get setup properly. This is because the speedtree asset is imported before the HDRP asset is imported, so the correct shader is not grabbed, and the correct postprocessing is not run. This is a recurring issue and topic of discussion not unique to SpeedTree, so it should not be blocking for this PR.

For URP, tested that manually switching over the shader works as expected. No upgrader or importer support for the shadergraph is needed yet as it is not yet the default shader.

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Comments to reviewers

@LandonTownsendUnity do you mind checking if the normal flipping is behaving as you'd expect in HDRP?
@adrien-de-tocqueville for changes to HDShaderUtils.ResetMaterialKeywords.
@cdxntchou for placement of files within shadergraph and core packages. Notably, LODCrossfade is not specific to SpeedTree. Maybe it should be placed someplace else/exposed generally somehow?
@phi-lira for feedback on adding the shadergraph to Universal and not hooking it up since it's not intended to replace the default yet.

[adrien-de-tocqueville]

the material keyword reset code lgtm

[kroatoa]

Am I right in assuming that this PR effectively targets 19.4?
I don't see any mention of this having landed in branches targeting the later versions, how is that tracked?

[nerites]

@kroatoa Since shadergraph is not backwards compatible, I started with 19.4 and am making PRs for later versions as I get them ready. I will have a 20.2 PR up later today, but it's not tracked anywhere outside my worklog for now. :)

[nerites]

10.x.x version here. No changes from 7.x.x. #3861

[kroatoa]

Thanks for clarifying

[nerites]

@kroatoa I have some API changes that will require incrementing package versions for Core and HDRP. How do I decide whether to increment minor or major versions? Who do I need to get approval from for incrementing the versions of those packages?

[phi-lira]

Did the PR to master landed? I can only find this one but it was closed: #3713

[nerites]

@phi-lira No, I am remaking it. I can have a new PR to master up today. I started with 19.4 since Shadergraph isn't backwards compatible, so it was easier to work from 19.4 and go forward.

[kroatoa]

@kroatoa I have some API changes that will require incrementing package versions for Core and HDRP. How do I decide whether to increment minor or major versions? Who do I need to get approval from for incrementing the versions of those packages?

Please reach out to the RM for the branch you are targeting. if it's more than one you can also put a post in #release-management, and we'll take it from there.

[nerites]

After some discussion with other folks, I'm only targeting 10.x.x and latest. PRs here:
10.x.x: #3861
Latest: #3911