CI: Add ROCm nightly docker workflow

[leo-amd]

Motivation

Migrating from Jenkins. This PR adds ROCm-specific nightly docker automation so we can build and validate a dedicated ROCm nightly image outside the standard PyTorch docker release flow

Technical Details

• Adds .github/workflows/pytorch-nightly-docker.yml to build and push a ROCm nightly image, support an optional rocm_version override, and run a ROCm smoke-test job against the produced image.
• Adds .ci/docker/pytorch-nightly-docker.Dockerfile to build PyTorch, torchvision, and torchaudio on top of the ROCm nightly base image.

Test Result

[rocm-repo-management-api]

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[rocm-repo-management-api]

Jenkins build for 2a6a9e6614cfbebfa7dfe3d00ab916b1cbad280c commit finished as NOT_BUILT
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[rocm-repo-management-api]

Jenkins build for c818f73ca711707fc670b9d6ec75a9ed87a5da3d commit finished as NOT_BUILT
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[rocm-repo-management-api]

Jenkins build for c818f73ca711707fc670b9d6ec75a9ed87a5da3d commit finished as FAILURE
Links: Pipeline Overview / Build artifacts / Test Results

[rocm-repo-management-api]

Jenkins build for 03393e9a469aa02ae29a993e1fe0a035892b9bfb commit finished as NOT_BUILT
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[rocm-repo-management-api]

Jenkins build for 551548d9a1789875c999ce3723ccf7cdc51ae8a9 commit finished as NOT_BUILT
Links: Pipeline Overview / Build artifacts / Test Results

[rocm-repo-management-api]

Jenkins build for 551548d9a1789875c999ce3723ccf7cdc51ae8a9 commit finished as FAILURE
Links: Pipeline Overview / Build artifacts / Test Results