NTSTATUS and HRESULT projected as struct instead of enum

Is your feature request related to a problem? Please describe.
Unlike WIN32_ERROR, NTSTATUS and HRESULT are projected as structs instead of enums. As individual error codes are not constant expressions, they cannot be used in switch statements:

if (status == NTSTATUS.STATUS_SUCCESS || status == NTSTATUS.STATUS_PENDING || status == NTSTATUS.STATUS_MORE_ENTRIES || status == NTSTATUS.STATUS_BUFFER_TOO_SMALL)
{
    // No error occurred, so exit gracefully.
    return status;
}

if (status == NTSTATUS.STATUS_INVALID_PARAMETER)
{
    throw new ArgumentException();
}

Describe the solution you'd like
With enums, switch statements can be used, which simplifies the code:

switch (error)
{
    case WIN32_ERROR.ERROR_DS_INVALID_DN_SYNTAX:
    case WIN32_ERROR.ERROR_INVALID_PARAMETER:
    case WIN32_ERROR.ERROR_INVALID_NAME:
    case WIN32_ERROR.ERROR_BAD_ARGUMENTS:
    case WIN32_ERROR.ERROR_INVALID_FLAG_NUMBER:
    case WIN32_ERROR.ERROR_INVALID_ADDRESS:
        exceptionToThrow = new ArgumentException(genericException.Message, genericException);
        break;
    case WIN32_ERROR.ERROR_ARITHMETIC_OVERFLOW:
        exceptionToThrow = new ArithmeticException(genericException.Message, genericException);
        break;
    case WIN32_ERROR.ERROR_BAD_EXE_FORMAT:
        exceptionToThrow = new BadImageFormatException(genericException.Message, genericException);
        break;
    case WIN32_ERROR.ERROR_BAD_FORMAT:
    case WIN32_ERROR.ERROR_SXS_MANIFEST_PARSE_ERROR:
    case WIN32_ERROR.ERROR_INVALID_DATA:
    case WIN32_ERROR.ERROR_DATATYPE_MISMATCH:
        exceptionToThrow = new FormatException(genericException.Message, genericException);
        break;
...
}

Start by tracing how NTSTATUS and HRESULT are projected and compare that path with the existing WIN32_ERROR enum projection. Determine the generator entry point and related tests from those type names; done means generated NTSTATUS and HRESULT values can be used in C# switch statements without breaking existing projections.