OccBin tools: rework codes

See merge request !2251

Ref. !2265

Ref. !2264

Ref. !2262

required for some symbols users regularly use

preprocessor increments lags/leads always only by lead_lag

transformed steady state is not passed back anymore

Ref. !2256

The implicit conversion from Vector to ConstVector, in addition to the
rewriting rules and ConstVector::operator<=>, ensure that those are no longer
needed.

Those are no longer needed thanks to expression rewriting.

Ref. !2260

Also minor improvements to solve_algo description.

[skip ci]

Ref. !2259

Ref. !2258

Ref. !2257

Also removes eval

one was empty, the other was moved to an inline function