Add sdxl and faceid docker containers

[victorges]

What does this pull request do? Explain your changes. (required)
This pull request adds support for two new StreamDiffusion variants, streamdiffusion-sdxl and streamdiffusion-sdxl-faceid, by mapping them to their respective Docker images in the ai/worker/docker.go file. This enables the system to correctly identify and launch these new live pipeline containers.

Specific updates (required)

• Added streamdiffusion-sdxl to the livePipelineToImage map, pointing to livepeer/ai-runner:live-app-streamdiffusion-sdxl.
• Added streamdiffusion-sdxl-faceid to the livePipelineToImage map, pointing to livepeer/ai-runner:live-app-streamdiffusion-sdxl-faceid.
• Configured the new entries to mirror the existing streamdiffusion-sd15 pattern, including descriptive comments.

How did you test each of these updates (required)
The configuration style for the new entries was verified by inspecting the git commit history that introduced the streamdiffusion-sd15 variant to ensure consistency. The project was built locally to confirm that the changes compile successfully.

Does this pull request close any open issues?

Checklist:

• Read the contribution guide
• make runs successfully
• All tests in ./test.sh pass
• README and other documentation updated
• Pending changelog updated

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[cursor]

Cursor Agent can help with this pull request. Just @cursor in comments and I'll start working on changes in this branch.
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