Wrap Sendability warning for OpaquePointer

[blindspotbounty]

According to proposal https://github.com/apple/swift-evolution/blob/main/proposals/0331-remove-sendable-from-unsafepointer.md OpaquePointer is no longer Sendable (also comment)

Let's fix that by wrapping it or by setting @unchecked Sendable