make sure also ALL updated variables in period 1 are reconstructed with smoother_redux. test model changed accordingly.

eliminate buggy and useless check for existence of guess regime variable. this may create bugs in running PKF update step!

adjust smoother redux test, to consider that now ALL smoothed variables must be properly reconstructed also in period 1

- allow having binding regimes in period 1 with occbin
- further improve recovering of smoothed variables in period 1 under smoother_redux option

[skip ci]

Use the new time-recursive block decomposition computed by the preprocessor
for:
- the simulation of backward models with “simul_backward”
- the perfect foresight simulation of purely backward/forward/static models

Also note that in this case, the preprocessor now defaults to “mfs=3” (i.e. it
minimizes the set of feedback variables and tries to renormalize equations).

This replaces the previous algorithm based on Dulmage-Mendelsohn (dmperm), plus
an ad hoc identification of some equations that can be evaluated (those with a
LHS equal to a variable, the log of a variable, or the diff-log of a variable).

By the way, the block_trust_region MEX has been modified so that it accepts a
boolean argument to decide whether it performs a Dulmage-Mendelsohn
decomposition (if not, then it performs a simple trust region on the whole
nonlinear system).

This provides a significant performance improvement (of almost an order of
magnitude for solve_algo=14 on a 700 equations model).

If the function to be solved returns a sparse Jacobian, simply convert it to a
dense representation.

sim1.m: use operation that preserves sparsity

See merge request !2111

Ref. !2019

Ref. !2110

Was crashing if the auxiliary model contains a constant.

See https://forum.dynare.org/t/iterative-ols-for-pac-equation/21379.

Fix: scale the matrices in tests/riccatiupdate.m to control the size of errors

See merge request !2108

Ref. !2105

Ref. !2103