[test][2p] Add test with gmsh grid file

We only have one gridcreator test using gmsh files. This adds
another one. The grid ordering changes and the fuzzy compare
could not sort it correctly. Might need a fix there. The
solution is identical. Update reference.

test/porousmediumflow/2p/implicit/grids/rectangle-domain.geo

+// Rectangular structured cube grid
+// compile with gmsh -2 rectangle-domain.geo
+
+Point(1) = {0, 0, 0, 1.0};
+Point(2) = {6, 0, 0, 1.0};
+Point(3) = {6, 4, 0, 1.0};
+Point(4) = {0, 4, 0, 1.0};
+Line(1) = {4, 3};
+Line(2) = {3, 2};
+Line(3) = {2, 1};
+Line(4) = {1, 4};
+Line Loop(6) = {1, 2, 3, 4};
+Plane Surface(7) = {6};
+
+Transfinite Line{1, 3} = 49; // 48 cells
+Transfinite Line{2, 4} = 33; // 33 cells
+Transfinite Surface{7}; // structured surface
+Recombine Surface{7}; // make quarilateral

test/porousmediumflow/2p/implicit/test_ccadaptive2p.input

@@ -3,9 +3,7 @@ DtInitial = 250 # [s]
 TEnd = 3000 # [s]
 
 [Grid]
-LowerLeft = 0 0
-UpperRight = 6 4
-Cells = 48 32
+File = ./grids/rectangle-domain.msh
 
 [SpatialParams]
 LensLowerLeftX = 1.0 # [m] x-coordinate of the lower left lens corner