Update sample CSS policy to handle multiple products and allow higher TCB values

[achamayou]

No substantial performance impact compared to values on main: https://bencher.dev/console/projects/scitt-ccf-ledger/plots

    "Register Signed Statement ppe_css": {
        "latency": {
            "value": 4038114.547729492,
            "high_value": 4177570.343017578,
            "low_value": 3933429.718017578
        }
    },

(Numbers in nanoseconds)