As pointed out by @Stan in D2529, it is unbalanced you can train champion cavalry only at some but not all barracks. This patch inserts the barracks champions in the production list of the shared parent, which means that players who've researched the unlock champions technology can train their champions at any captured enemy barracks, regardless the civ who built it, thus improving balance.
Likewise, it's unnecessary to specify the unlock_champion_units and upgrade_rank_advanced_mercenary in individual specific barracks, because those technologies specify the civs that can research it in the technology files; cf. D1941/rP22329.
Furthermore, it moves `mace_champion_infantry_a_barracks.xml` to `mace_champion_infantry_barracks.xml` and deletes `mace_champion_infantry_e_barracks.xml`, so Macedon can train them at captured enemy barracks and enemies can train theirs at mace barracks.