WIP: perfect foresight controlled paths

TODO:
– add test that checks that computed exos actually give the requested endos
  when doing a regular simulation
– add test to check that a given exo is not simultaneously in
  perfect_foresight_controlled_paths and shocks, or that a given exo/endo does
  not appear two times in perfect_foresight_controlled_paths for a given period
– support perfect_foresight_with_expectation_errors (+test)
– support homotopy (+test) (+linearization?)
– support LBJ (+test)
– support stack_solve_algo=7 (reusing function for stacked Jacobian substitution)
– integrate all tests in meson
– documentation

[skip ci]