stats: explicitly instantiate the template class DataCalculator<uint32_t> to prevent duplicate TypeId registration

Spin-off of !437 (merged)

This patch prevents the following error:

H:\tools\source\ns-3-dev>python3 ns3 run "wifi-example-sim"                   
[0/2] Re-checking globbed directories...
ninja: no work to do.
assert failed. cond="m_namemap.count (name) == 0", msg="Trying to allocate twice the same uid: ns3::CounterCalculator<uint32_t>", +0.000000000s -1 file=H:/tools/source/ns-3-dev/src/core/model/type-id.cc, line=387
terminate called without an active exception
Command 'build/examples/stats/ns3-dev-wifi-example-sim-debug.exe' returned non-zero exit status 3.