Werk #10767: Implement Forecast Graph prediction engine

To avoid the need for extenal dependencies for the Forecasting Graphs Checkmk now ships its own implementation of the prediction algorithm.

This Werk replaces Werk #7451. The script {bin/install_fbprophet} available in Checkmk 1.6 can be used to unistall the external dependencies before updating to Checkmk 2.0. Once updated to Checkmk 2.0 which also uses Python3 as default, no script can be provided to clean up python2 runtime dependecies. As such the user is advised to manually remove the unused contents of his local folders in {local/lib/python}

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