[RF] Introducing binned likelihood fit optimization in HistFactory

In a binned likelihood fit, it is possible to skip the PDF normalization
when the unnormalized binned PDF can be interpreted directly in terms of
event yields. This is now done by default for models HistFactory models,
which results in great speedups for binned fits with many channels. Some
RooFit users like ATLAS were already using this for a long time, so this
feature is battle-tested.

To disable this optimization when using the `hist2workspace` executable,
add the `-disable_binned_fit_optimization` command line argument.
Directly in C++, you can also set the `binnedFitOptimization` to `false`
in the HistFactory configuration as follows:
```C++
RooStats::HistFactory::MakeModelAndMeasurementFast(measurement, {.binnedFitOptimization=false});
```
If your compiler doesn't support aggregate initialization with designators, you
need to create and edit the configuration struct explicitely:
```C++
RooStats::HistFactory::HistoToWorkspaceFactoryFast::Configuration hfCfg;
hfCfg.binnedFitOptimization = false;
RooStats::HistFactory::MakeModelAndMeasurementFast(measurement, hfCfg);
```