Fix bug in `make_covariates`

Fixes bug in make_covariates as pushed in release 2.3.0. This bug occurred when the user was creating covariates based on the new formula interface (which hopefully had not seen much use yet) and covariate_data were not ordered with respect to year. I have added a new integrated-test that checks intercept and slope estimates using the conventional lognormal delta-model without any random effects (i.e., no spatial or spatio-temporal terms) against two separate lognormal and logistic GLMs fitted using stats::glm(.), so results using the formula interface are more carefully maintained in future releases.