Restoring and relocating CoSAI practical guide patterns

[rabbidave]

Restores the four files that were previously reverted from the root directory, relocating them into a new, structured practical-guides/ directory. The content remains byte-identical to the original commit, with the exception of the filename change for artifact-integrity-maturity.cosai-rm.yaml to match the correct extension.

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[rabbidave]

having issues with the CLA not showing that I've already signed