Introduce proper check for stochastic singularity
initial_estimation_checks we should introduce a proper check for stochastic singularity by setting
options_.use_univariate_filters_if_singularity_is_detected=0 and then providing an informative error message when
info(1) == 50.
This prevents user errors where the model has a fundamental stochastic singularity, because Dynare by default will resort to the univariate filter without warning.