[Eva] use vorig_name in feedback to minimize noise due to Variadic renaming

src/plugins/eva/engine/compute_functions.ml

.../declared/oracle/redefine_anonymous_parameters.res.oracle

src/plugins/variadic/tests/known/oracle/exec.res.oracle

src/plugins/variadic/tests/known/oracle/fcntl.res.oracle

src/plugins/variadic/tests/known/oracle/open.res.oracle

...plugins/variadic/tests/known/oracle/open_wrong.res.oracle

src/plugins/variadic/tests/known/oracle/openat.res.oracle

src/plugins/variadic/tests/known/oracle/printf.res.oracle

...variadic/tests/known/oracle/printf_garbled_mix.res.oracle

...s/variadic/tests/known/oracle/printf_redefined.res.oracle

...variadic/tests/known/oracle/printf_wrong_arity.res.oracle

...iadic/tests/known/oracle/printf_wrong_pointers.res.oracle

...variadic/tests/known/oracle/printf_wrong_types.res.oracle

src/plugins/variadic/tests/known/oracle/scanf.0.res.oracle

src/plugins/variadic/tests/known/oracle/scanf.1.res.oracle

...plugins/variadic/tests/known/oracle/scanf_loop.res.oracle

src/plugins/variadic/tests/known/oracle/snprintf.res.oracle

src/plugins/variadic/tests/known/oracle/swprintf.res.oracle

src/plugins/variadic/tests/known/oracle/wchar.res.oracle

tests/builtins/oracle/linked_list.0.res.oracle