ADIOS2 Bool: Dataset Support

**Describe the bug**
It looks like `bool` types are currently only supported for attributes with our ADIOS2 backend.
Adding support for types with the same convention should be added, too.

**To Reproduce**

```C++
#include

#include
#include
#include
#include
#include

using std::cout;
using namespace openPMD;

int main(int argc, char *argv[])
{
// user input: size of matrix to write, default 3x3
size_t size = (argc == 2 ? atoi(argv[1]) : 3);

// matrix dataset to write with values 0...size*size-1
std::array global_data;
//std::iota(global_data.begin(), global_data.end(), 0.);

cout << "Set up a 2D square array (" << size << 'x' << size
<< ") that will be written\n";

// open file for writing
Series series = Series(
"../samples/3_write_serial.bp",
Access::CREATE
);
cout << "Created an empty " << series.iterationEncoding() << " Series\n";

MeshRecordComponent rho =
series
.iterations[1]
.meshes["rho"][MeshRecordComponent::SCALAR];
cout << "Created a scalar mesh Record with all required openPMD attributes\n";

Datatype datatype = determineDatatype();
Extent extent = {size, size};
Dataset dataset = Dataset(datatype, extent);
cout << "Created a Dataset of size " << dataset.extent[0] << 'x' << dataset.extent[1]
<< " and Datatype " << dataset.dtype << '\n';

rho.resetDataset(dataset);
cout << "Set the dataset properties for the scalar field rho in iteration 1\n";

series.flush();
cout << "File structure and required attributes have been written\n";

Offset offset = {0, 0};
rho.storeChunk(shareRaw(global_data), offset, extent);
cout << "Stored the whole Dataset contents as a single chunk, "
"ready to write content\n";

series.flush();
cout << "Dataset content has been fully written\n";

/* The files in 'series' are still open until the object is destroyed, on
* which it cleanly flushes and closes all open file handles.
* When running out of scope on return, the 'Series' destructor is called.
*/
return 0;
}
```

```
Set up a 2D square array (3x3) that will be written
Created an empty groupBased Series
Created a scalar mesh Record with all required openPMD attributes
Created a Dataset of size 3x3 and Datatype BOOL
Set the dataset properties for the scalar field rho in iteration 1
terminate called after throwing an instance of 'std::runtime_error'
what(): [ADIOS2] Trying to access dataset with unallowed datatype: BOOL
Aborted (core dumped)
```

**Expected behavior**
Let's apply the same convention as for attributes.

In order to avoid naming collisions, I would propose keep using `__is_boolean__/` as prefix for the identifier for attributes and use another one, `__is_boolean_var__/` for ADIOS variables.

**Software Environment**
- version of openPMD-api: 0.13.2
- installed openPMD-api via: from source
- operating system: Ubuntu 20.04
- machine: laptop
- name and version of Python implementation: N/A
- version of HDF5: N/A
- version of ADIOS1: N/A
- version of ADIOS2: 2.6.0
- name and version of MPI: N/A

**Additional context**

In PIConGPU, we always just mapped bools to `adios_unsigned_byte` in ADIOS1 (BP3): https://github.com/ComputationalRadiationPhysics/picongpu/pull/1756
This naturally means we cannot round-trip the type (we had no identifier).

I believe that for @PrometheusPi's particle mask flags with openPMD-api (radiation plugin), we do the same work-around at the moment. cc @franzpoeschel