Extract Woodbury engine from DC sensitivity analysis (#1064)

Signed-off-by: p-arvy <pierre.arvy@artelys.com>
Co-authored-by: Anne Tilloy <anne.tilloy@rte-france.com>
Co-authored-by: Hadrien <hadrien.godard@artelys.com>

src/main/java/com/powsybl/openloadflow/sensi/AbstractSensitivityAnalysis.java

@@ -101,10 +101,6 @@ enum Status {
 
         void setFunctionReference(double functionReference);
 
-        double getBaseSensitivityValue();
-
-        void setBaseCaseSensitivityValue(double baseCaseSensitivityValue);
-
         Status getStatus();
 
         void setStatus(Status status);
@@ -142,8 +138,6 @@ protected abstract static class AbstractLfSensitivityFactor<V extends Enum<V> &
 
         private double functionReference = 0d;
 
-        private double baseCaseSensitivityValue = Double.NaN; // the sensitivity value on pre contingency network, that needs to be recomputed if the stack distribution change
-
         protected Status status = Status.VALID;
 
         protected SensitivityFactorGroup<V, E> group;
@@ -263,16 +257,6 @@ public void setFunctionReference(double functionReference) {
             this.functionReference = functionReference;
         }
 
-        @Override
-        public double getBaseSensitivityValue() {
-            return baseCaseSensitivityValue;
-        }
-
-        @Override
-        public void setBaseCaseSensitivityValue(double baseCaseSensitivityValue) {
-            this.baseCaseSensitivityValue = baseCaseSensitivityValue;
-        }
-
         @Override
         public Status getStatus() {
             return status;

src/main/java/com/powsybl/openloadflow/sensi/ComputedContingencyElement.java

@@ -28,8 +28,7 @@ public final class ComputedContingencyElement {
 
     private int contingencyIndex = -1; // index of the element in the rhs for +1-1
     private int localIndex = -1; // local index of the element : index of the element in the matrix used in the setAlphas method
-    private double alphaForSensitivityValue = Double.NaN;
-    private double alphaForFunctionReference = Double.NaN;
+    private double alphaForPostContingencyState = Double.NaN;
     private final ContingencyElement element;
     private final LfBranch lfBranch;
     private final ClosedBranchSide1DcFlowEquationTerm branchEquation;
@@ -56,20 +55,12 @@ private void setLocalIndex(final int index) {
         this.localIndex = index;
     }
 
-    public double getAlphaForSensitivityValue() {
-        return alphaForSensitivityValue;
+    public double getAlphaForPostContingencyState() {
+        return alphaForPostContingencyState;
     }
 
-    public void setAlphaForSensitivityValue(final double alpha) {
-        this.alphaForSensitivityValue = alpha;
-    }
-
-    public double getAlphaForFunctionReference() {
-        return alphaForFunctionReference;
-    }
-
-    public void setAlphaForFunctionReference(final double alpha) {
-        this.alphaForFunctionReference = alpha;
+    public void setAlphaForPostContingencyState(double alphaForPostContingencyStates) {
+        this.alphaForPostContingencyState = alphaForPostContingencyStates;
     }
 
     public ContingencyElement getElement() {