EB Boundary Area: Fix issues for anisotropic cell size

* In 2D, the scaling in incorrect. For example, if dx >> dy and the boundary
  is parallel to the x-direction, it would produce inf for the scaled
  boundary area.

* In 3D, the scaling has been modified so that it's easy to convert from the
  dimensionless boundary area to physical units.

Src/EB/AMReX_EB2_2D_C.cpp

@@ -30,8 +30,7 @@ void set_eb_data (const int i, const int j,
  const Real apnorm = std::hypot(daxp,dayp) + 1.e-30_rt*std::sqrt(dx[0]*dx[1]);
  const Real nx = daxp * (1.0_rt/apnorm);
  const Real ny = dayp * (1.0_rt/apnorm);
- const Real bareascaling = std::sqrt( (nx*dx[0])*(nx*dx[0]) +
- (ny*dx[1])*(ny*dx[1]) );
+ const Real bareascaling = std::sqrt(Math::powi<2>(nx*dx[1]) + Math::powi<2>(ny*dx[0]));
 
  const Real nxabs = std::abs(nx);
  const Real nyabs = std::abs(ny);

Src/EB/AMReX_EB2_3D_C.cpp

@@ -101,7 +101,9 @@ void set_eb_data (const int i, const int j, const int k,
  bnorm(i,j,k,0) = nx;
  bnorm(i,j,k,1) = ny;
  bnorm(i,j,k,2) = nz;
- barea(i,j,k) = (nx*dapx/(dx[1]*dx[2]) + ny*dapy/(dx[0]*dx[2]) + nz*dapz/(dx[0]*dx[1]));
+ barea(i,j,k) = (nx*dapx + ny*dapy + nz*dapz) / (Math::powi<2>(nx*dx[1]*dx[2]) +
+ Math::powi<2>(ny*dx[0]*dx[2]) +
+ Math::powi<2>(nz*dx[0]*dx[1]));
 
  Real aax = 0.5_rt*(axm+axp);
  Real aay = 0.5_rt*(aym+ayp);