irf_matching: Add CET (2016, Econometrica) test

meson.build

tests/estimation/method_of_moments/CET/cet_data.mat

tests/estimation/method_of_moments/CET/cet_imh.mod

.../estimation/method_of_moments/CET/cet_irf_matching_file.m

...of_moments/CET/cet_matched_irfs_no_interface_workaround.m

tests/estimation/method_of_moments/CET/cet_mle.mod

tests/estimation/method_of_moments/CET/cet_model.inc

tests/estimation/method_of_moments/CET/cet_original_mode.mat

tests/estimation/method_of_moments/CET/cet_rwmh.mod

tests/estimation/method_of_moments/CET/cet_slice.mod

tests/estimation/method_of_moments/CET/cet_steady_helper.m

tests/estimation/method_of_moments/CET/cet_tarb.mod