powsybl-open-loadflow [WIP] Reduce time spent in eval and der in equation resolution

This PR implements the idea of #778 (that is minimizing memory cache misses during equation eval and der) in a way that is compatible with the current equation model and that keeps its properties (code isolation, lazy evaluation when done outside of NR, object model).

Results

Computation time divided by 1.8

Der and eval are no longer the top hotspot in a Security Analysis

Before: With the PR:

Implementation

A VectorEngine is in charge of computing eval and der used in the NR resolution. The optimization is performed on branch equations. To minimize cache misses, the terms are sorted element type, element num (which is most often a branch), equation element num (wich is most often a bus), then by bus, then by variable (for der operations). Branch data is stored in a unique array ordered by branch num. To avoid loading small objects (like terms and equations), their active status and equation columns are replicated via the notification system in an ordered array. Some terms provide static interfaces called VecToVal that enable to compute derivatives or evalLhs without loading the term object. This is done at this time for close branch equations on P and Q. Branch typical values (sinksi, costhetha1, costheta2 etc..) are computed only once per branch.

Known issues

Probably remaining memory cach miss due to the network structure (hard to visit at the same time branch and bus in the data roder)
Two tests currently deactivated. Need investigation and resolution. Please check if the PR fulfills these requirements