Review obsolete cached PublicKey.Key access (SYSLIB0027)

Find only resolved BCL PublicKey.Key properties. Review algorithm-specific public-key access while preserving algorithm support, null/exception behavior, cached key identity and disposal ownership. The old property caches RSA/DSA keys and rejects other algorithms; algorithm-specific methods can return fresh keys, null or newly supported algorithms. No API, algorithm or lifetime policy is selected. Other properties, lookalikes, unresolved accesses and conditional snapshots remain unchanged. Opt-in review only.