perf(linear-vesting): optimize validator with raw BI.* data extraction

Replace high-level pattern matching with raw BI.unsafeDataAsConstr,
BI.head/tail for data extraction, BI.caseList' for list traversal,
and BI.caseInteger for redeemer dispatch. Use standard Haskell
multi-way if guards instead of builtinIf pattern.

CPU: 30.4M → 11.4M (62% reduction)
MEM: 129K → 48K (63% reduction)

Author: Unisay