The Transfer aesop rule set — declaration module

A rule set declared with declare_aesop_rule_sets is not visible in the file that declares it (aesop's frontend only exposes it to importing files — the reason Mathlib keeps each set in a tiny Init.lean). This module only declares the set, so that Transfer/Integrations/AesopIntegration.lean (which imports it) can register rules into it and invoke aesop (rule_sets := [Transfer]), and so the named set is usable engine-wide by any downstream file.