Validation for RobinCar2 compared to RobinCar

[mbannick]

This PR creates tests to compare RobinCar2 outputs to RobinCar. It also proposes changes to the RobinCar2 code to enable the tests where needed. The two things being compared are the estimates and the estimated variances.

[github-actions]

Unit Test Performance Difference

Test Suite	$Status$	Time on main	$±Time$	$±Tests$	$±Skipped$	$±Failures$	$±Errors$
validate-robin_glm	👶		$+1.25$	$+6$	$0$	$+6$	$0$

Additional test case details

Test Suite	$Status$	Time on main	$±Time$	Test Case
utils	💀	$0.03$	$-0.03$	h_get_vars_works_for_formula_with_schemas
utils	👶		$+0.04$	h_get_vars_works_for_single_character
validate-robin_glm	👶		$+1.25$	simple_randomization_difference_contrast
variance	💀	$0.03$	$-0.03$	gvcov_works
variance	👶		$+0.03$	vcovANHECOVA_works

Results for commit 7c57671

♻️ This comment has been updated with latest results.

[github-actions]

Code Coverage Summary

Filename                     Stmts    Miss  Cover    Missing
-------------------------  -------  ------  -------  -----------------
R/bias.R                        11       0  100.00%
R/predict_couterfactual.R       47       0  100.00%
R/prediction_cf.R                3       0  100.00%
R/robin_glm.R                   27       0  100.00%
R/treatment_effect.R           100       7  93.00%   30, 43, 65-69, 81
R/utils.R                       21       1  95.24%   16
R/variance_anhecova.R           45      18  60.00%   30, 45-46, 65-80
R/variance_hc.R                  9       0  100.00%
TOTAL                          263      26  90.11%

Diff against main

Filename                 Stmts    Miss  Cover
---------------------  -------  ------  -------
R/treatment_effect.R        +1       0  +0.07%
R/variance_anhecova.R        0      -1  +2.22%
TOTAL                       +1      -1  +0.42%

Results for commit: cb4ad54

Minimum allowed coverage is 80%

♻️ This comment has been updated with latest results

[github-actions]

Unit Tests Summary

 1 files   7 suites   2s ⏱️
21 tests 13 ✅ 7 💤 1 ❌
62 runs  48 ✅ 8 💤 6 ❌

For more details on these failures, see this check.

Results for commit 12ae3f3.