Implement {U,V}TEND_{DCONV,SHCONV,...} tendency diagnostics - vertical diffusion

In `physpkg.F90` in current CAM there are a few blocks of additional `outfld` calls after each `_tend` call.

e.g., for vertical diffusion,

```fortran
call addfld ( 'UTEND_VDIFF', (/ 'lev' /), 'A', 'm/s2', 'Zonal wind tendency by vert. diffus.')
call addfld ( 'VTEND_VDIFF', (/ 'lev' /), 'A', 'm/s2', 'Meridional wind tendency by vert. diffus.')
call register_vector_field ( 'UTEND_VDIFF', 'VTEND_VDIFF')
```

and
```fortran
...
if ( (trim(cam_take_snapshot_after) == "vertical_diffusion_section") .and. &
(trim(cam_take_snapshot_before) == trim(cam_take_snapshot_after))) then
call cam_snapshot_ptend_outfld(ptend, lchnk)
end if
if ( ptend%lu ) then
call outfld( 'UTEND_VDIFF', ptend%u, pcols, lchnk)
end if
if ( ptend%lv ) then
call outfld( 'VTEND_VDIFF', ptend%v, pcols, lchnk)
end if
```

this seems to be for "budget" diagnostics.

This issue serves as a reminder that these little parts of `physpkg.F90` might need to be added in the future; the best place to have these diagnostics would probably be before the tendency updater runs for the respective CCPP'ized schemes.

Note that some of these might already be output elsewhere and thus may be duplicates. Just that `physpkg.F90` has a "systematic" set of code to output these U/V tendencies.