Accepts either a single PKESchemeFeature enum value or a
uint32_t bitwise-OR mask of PKESchemeFeature values (for
surface parity with the C++ Enable(uint32_t) overload). The two paths
dispatch on the value itself: a mask is detected by being
strictly larger than the largest single-feature value
(Feature$SCHEMESWITCH = 0x80 = 128) or by having more than one
bit set.