runFinal improvements

[jalimena]

This PR adds a few options when running fccanalysis final analysis_final.py, namely:

1. The option to scale the number of events printed after each selection by the target integrated luminosity and the cross section (by introducing new variables called intLumi and doScale)
2. The option to save the number of events (scaled or not) and their uncertainties in a latex table (with the variable saveTabular)
3. The option to rename the selections in an easier-to-read way for that table (with the variable cutLabels)

An example of how to use these new variables is provided in examples/FCCee/bsm/LLPs/DisplacedHNL/analysis_final.py

[jalimena]

tagging @vvolkl and @clementhelsens thanks!

[vvolkl]

Looks good to me, thanks a lot! Waiting for Clement to take a look as well.

[clementhelsens]

thanks @jalimena , looks good. sorry for late actions, we are in the middle of the hands on tuto

[jalimena]

thanks! yeah no worries, hope the tutorial is going well!