[flang][HLFIR] unimplemented symbol lowering

[tblah]

Some programs from the Fujitsu test suite hit not yet implemented: lowering symbol to HLFIR:

• https://github.com/fujitsu/compiler-test-suite/blob/main/Fortran/0115/0115_0009.F90
• https://github.com/fujitsu/compiler-test-suite/blob/main/Fortran/0115/0115_0010.F90
• https://github.com/fujitsu/compiler-test-suite/blob/main/Fortran/0115/0115_0011.F90

Here is a minimal reproducer:

subroutine sub1(dest1, dest2, src1, src2)
  real, dimension(1:2)::dest1, dest2, src1, src2
  integer::i

  do i=1,2
     block
       dest1(i) = src1(i) * src2(i) + src1(i) * src2(i)
     end block
  end do
end subroutine sub1

subroutine sub2(dest1_res, dest2_res, src1_res, src2_res)
  real(kind=8),dimension(1:2)::dest1_res, dest2_res, src1_res, src2_res
end subroutine sub2

@jeanPerier is this expected? I was surprised to see a HLFIR TODO