Do not expand APPLY_SELECTOR (#8174)

Do not expand APPLY_SELECTOR (#8174)

Currently we expand (sel_C_n x) to (ite (is-C x) (sel_C_n_total x) (uf x)) during ppRewrite. This introduces ITEs very eagerly and moreover is not necessary since we do congruence over selectors.

This makes it so that we don't do this expansion. The code changes to use APPLY_SELECTOR everywhere instead of APPLY_SELECTOR_TOTAL, which can be deleted in a followup PR. It makes some of the datatype utilities more robust and independent of options.

This required changing one detail of the sygus solver to not do evaluation unfolding in cases where a selector chain was wrongly applied, as this now will not rewrite to a constant.