[Flang] Support for procedure pointer component default initialization. (#87356)

This PR is to address `TODO(loc, "procedure pointer component default
initialization");`.
It handles default init for procedure pointer components in a derived
type that is 32 bytes or larger (Default init for smaller size type has
already been handled).

```
  interface
    subroutine sub()
    end
  end interface
  type dt
    real :: r1 = 5.0
    procedure(real), pointer, nopass :: pp1 => null()
    real, pointer :: rp1 => null()
    procedure(), pointer, nopass :: pp2 => sub
  end type
  type(dt) :: dd1
  end

```