Remove unused known keys and names for natural operations
This removes the known-key and corresponding name variables for naturalAndNotIdKey, naturalLog2IdKey, naturalLogBaseWordIdKey, naturalLogBaseIdKey, naturalPowModIdKey, naturalSizeInBaseIdKey, naturalToFloatIdKey, and naturalToDoubleIdKey, as they are apparently nowhere used in GHC’s source code, and thus resolves part of #26677 (closed).