Reaction EFT: a new interface to fit SM/EFT parameters in the xFitter

A new reaction (EFT) is added. This reaction aims to fit SM or EFT parameters (together with PDF parameters) using polynomial approximation (Taylor series). The coefficients of these polynomials have to been calculated outside xFitter and fed to EFT reaction via an EFT yaml file. An example to fit the top quark pole mass to inclusive ttbar cross sections is also provided.

UPDATE 2024.07.22 Alternative example (EFT-thexp) is added which uses only theory interface and produces identical results.