ci : migrate ggml ci to self-hosted runners (#16116)
* ci : migrate ggml ci to a self-hosted runners
* ci : add T4 runner
* ci : add instructions for adding self-hosted runners
* ci : disable test-backend-ops from debug builds due to slowness
* ci : add AMD V710 runner (vulkan)
* cont : add ROCM workflow
* ci : switch to qwen3 0.6b model
* cont : fix the context size
