Align HunyuanVideoConditionEmbedding with CombinedTimestepGuidanceTextProjEmbeddings

[samutamm]

What does this PR do?

Recently 8907a70 replaced in HunyuanVideo pipeline CombinedTimestepGuidanceTextProjEmbeddings by improved embedding class HunyuanVideoConditionEmbedding. As a side-effect, the output conditioning = timesteps_emb + guidance_emb + pooled_projections became conditioning = timesteps_emb + pooled_projections + guidance_emb. This caused some tiny inconvenient differences in floating point operations and the output videos were altered.

This PR re-orders the addition of those tensors to be same as in CombinedTimestepGuidanceTextProjEmbeddings.

Fixes # (issue)
#12273

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@yiyixuxu @a-r-r-o-w

[a-r-r-o-w]

thanks!

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

[a-r-r-o-w]

cc @yiyixuxu

[eppaneamd]

@a-r-r-o-w @yiyixuxu any updates regarding merging this, any blockers? 👍

[samutamm]

cc @sayakpaul