remove dyn_time_lvls from all pbuf_add_field calls

### Issue Type

Code Clean-up

### Issue Description

dyn_time_lvls is for storing multiple time-levels in the pbuf, which was used to accommodate the EUL dycore. The EUL dycore was removed from the code, but there remains a large number of pbuf_add_fields calls that declare a dyn_time_lvls dimension, e.g.,

```
call pbuf_add_field('AST', 'global', dtype_r8, (/pcols,pver,dyn_time_lvls/), ast_idx)
```

this dimension should be removed from all pbuf variables. This simplifies the pbuf_get_field calls to exclude optional arguments ```start=(/1,1,itim_old/), kount=(/pcols,pver,1/)```.

### Will this change answers?

I Don't Know

### Will you be implementing this yourself?

No