Fix callers of group_chi2_table
Created by: Zaharid
Commit 79604bdb had introduced a level of indirection on the inputs of groups_chi2_table to make sure that the data wasn't being reshuffled too much. This however was not propagated to the actions that internally made use of that functionality, of which there are three.
Fix the simpler one to use the original action with the right grouping and add an additional collect over processes for the ones in the theory covariance matrix module.
Closes #1520 (closed).