Migrate Z->dilepton QEE lines to ThOr functors

Jianqiao Dengrequested to merge
ThOr_zmumu_zee into qee_upgrade

FYI @wbarter

This MR migrates the Z->mu mu (e e) and associated same-sign lines to ThOr. Rates and efficiencies were observed to be unchanged - please see discussion in !1348 (closed).

Supersedes !1348 (closed).

Edited by Ross Hunter

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