Provide a user-friendly version of queue construction from a device selector callable returning a `bool`

There are common use cases when a user wants to use a very precise device in her code and uses for example a boolean predicate to filter the device, like
```c++
sycl::queue { [](sycl::device dev) {
return "xilinx_u200_gen3x16_xdma_1_202110_1" == dev.template get_info();
} };
```
and to throw if there is no such device.
The problem is that in this code the returned `bool` is converted to an `int`, so when the device does exist it works because `true` is converted to `1`, but if it is not the case, `false` is converted to 0, so any other existing device is then equivalent, which is surprising.
To avoid this, the code has to be changed into something like
```c++
sycl::queue { [](sycl::device dev) {
return ("xilinx_u200_gen3x16_xdma_1_202110_1" == dev.template get_info()) - 1;
} };
```
to convert `0` or `1` to `-1` or `0` for example.

Having a different behavior for the `sycl::queue` constructor with a device selector returning a `bool` would be cleaner.

Start by reviewing the sycl::queue constructor and device selector behavior described in the issue, including how a callable returning bool is currently interpreted. Define the intended behavior for a bool-returning selector and update the relevant SYCL specification text; done means the documented construction no longer treats false as selecting an arbitrary device.

Written by the indexing model from the issue text.