ByteAddressBufferLoad<T> fails when T contains an enum value

[mcbouterse]

Templated ByteAddressBuffer loads will generate a compiler error if used to load a struct containing an enumeration value (Explicit template arguments on intrinsic Load must be a single numeric type). We currently work around this issue by storing enums as plain uint, but it would be nice if it would work with the enumeration type directly.

Sample Program: https://godbolt.org/z/GvGzb16Ej

Related to #4735