Cherry-pick Implementation of csin2_thetaW for SMEFTsim to master
The commit to be cherry-picked from rel-2-2-x to master is 4273e257.
Notes from the biweekly meeting agenda: "Anke (Frank K) sees some weird behaviour for the tilde operators, according to Marek this is normal for 22x. To be checked on Master. Stefan to help with debugging signs in the UFO implementation"
Edited by Enrico Bothmann