[examples] Clean linear solver scenes (sofa-framework#2494)

* [examples] MinResLinearSolver scene follows the same pattern

* [examples] speed up CGLinearSolver scene

Author: alxbilger

examples/Components/linearsolver/FEMBAR-CGLinearSolver.scn

@@ -2,7 +2,6 @@
     <RequiredPlugin name="SofaBoundaryCondition"/>
     <RequiredPlugin name="SofaImplicitOdeSolver"/>
     <RequiredPlugin name="SofaSimpleFem"/>
-    <RequiredPlugin name="SofaSparseSolver"/>
 
     <VisualStyle displayFlags="showBehaviorModels showForceFields" />
 
@@ -11,7 +10,7 @@
 
     <Node name="M1">
         <EulerImplicitSolver name="odesolver" rayleighStiffness="0.1" rayleighMass="0.1" />
-        <CGLinearSolver iterations="1000" threshold="1e-5" tolerance="1e-5"/>
+        <CGLinearSolver template="CompressedRowSparseMatrixMat3x3d" iterations="1000" threshold="1e-9" tolerance="1e-9"/>
         <MechanicalObject />
         <UniformMass vertexMass="1" />
         <RegularGridTopology nx="4" ny="4" nz="20" xmin="-9" xmax="-6" ymin="0" ymax="3" zmin="0" zmax="19" />

examples/Components/linearsolver/FEMBAR-MinResLinearSolver.scn

@@ -0,0 +1,21 @@
+<Node name="root" dt="0.02" gravity="0 -10 0">
+    <RequiredPlugin name="SofaBoundaryCondition"/>
+    <RequiredPlugin name="SofaImplicitOdeSolver"/>
+    <RequiredPlugin name="SofaSimpleFem"/>
+    <RequiredPlugin name="SofaGeneralLinearSolver"/>
+
+    <VisualStyle displayFlags="showBehaviorModels showForceFields" />
+
+    <DefaultAnimationLoop/>
+    <DefaultVisualManagerLoop/>
+
+    <Node name="M1">
+        <EulerImplicitSolver name="odesolver" rayleighStiffness="0.1" rayleighMass="0.1" />
+        <MinResLinearSolver template="GraphScattered" iterations="1000" tolerance="1e-9" />
+        <MechanicalObject />
+        <UniformMass vertexMass="1" />
+        <RegularGridTopology nx="4" ny="4" nz="20" xmin="-9" xmax="-6" ymin="0" ymax="3" zmin="0" zmax="19" />
+        <FixedConstraint indices="0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15" />
+        <HexahedronFEMForceField name="FEM" youngModulus="4000" poissonRatio="0.3" method="large" />
+    </Node>
+</Node>