Hepstats

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* sPlot: Increase the tolerance of the sanity check from 1e-3 to 5e-2, if above the tolerance a ModelNotFittedToData
exception is raised. In addition if the the check is above the 5e-3 tolerance a warning message is printed.

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* New documentation style
* **hepstats** can now do hypothesis tests, and compute upper limits and confidence intervals for counting analysis
* Progess bars are used to see the progression of the generation of the toys

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* ConfidenceInterval can compute Feldman and Cousin intervals with boundaries (i.e ``qtilde=True``)
* **AsymptoticCalculator** asymov weights are now scaled to the number of entries in dataset from loss
function if the loss is not extended
* **hepstats.hypotests** can now be used even if there is no nuisances. The **pll** function in **utils/fit/diverse.py**
had to be modified such that if there are no nuisances, the **pll** function returns the value of the loss function.
* add notebooks demos for FC intervals with the ``FrequentistCalculator`` and ``AsymptoticCalculator``.
* add warnings when multiple roots are found in ``ConfidenceInterval``
* move toys .yml files from notebook to notebook/toys

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* Redesigned packaging system, GHA deployment.
* **expected_poi** removed from **BaseCalculator** and **AsymptoticCalculator**
* add type checks in the **hypotests** submodule

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* **hepstats** is now compatible with zfit > 0.5 api
* expected intervals in upper limit are now calculated from the pvalues and not from the **expected_poi**
function anymore.

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* Addition of the **sPlot** algorithm