[WIP][AMD][MI355x] dsv4-fp4-mi355x-vllm-agentic, install latest lmcache

[ruizhang0101]

Summary

• Bump LMCache source build from pinned commit 9229067 to the v0.5.1 release tag (CXX=hipcc BUILD_WITH_HIP=1)
• Add --no-separate-object-group to the LMCache MP server launch command

[github-actions]

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[github-actions]

see unofficial run visualizer at https://inferencex.semianalysis.com/inference?unofficialRun=29375661761
see unofficial run visualizer at https://inferencex.semianalysis.com/evaluation?unofficialRun=29375661761

[github-actions]

see unofficial run visualizer at https://inferencex.semianalysis.com/inference?unofficialRun=29375704484
see unofficial run visualizer at https://inferencex.semianalysis.com/evaluation?unofficialRun=29375704484