add portable cache irritators stress-ng coverage

[Srikanth Muppandam (smuppand)]

This PR brings

• Add a portable Cache_Irritators suite using the public stress-ng interface.
• Exercise whole-cache, runtime-discovered cache-level, and optional TLB shootdown workloads.
• Support nominal, repeatability, and stress modes with configurable workers, operations, timeout, cache options, size, and ways.
• Detect supported stress-ng options dynamically instead of relying on distro or package-version checks.
• Add package mappings for Debian, Ubuntu, and CentOS while keeping Yocto image-managed.
• Add a Yocto LAVA definition with a single-line run.sh invocation.
• Retain per-workload logs, capability evidence, and kernel-log scan artifacts.