Do we need med_id?

There is a `med_id` variable that is set inside of the intenral state:
https://github.com/ESCOMP/CMEPS/blob/22dc297fa3f77cf1a232618f5428c89b460032ca/mediator/med_internalstate_mod.F90#L19

The use of component ids seems to be a carryover from before the NUOPC implementation. The med_id is only used in med_io_mod.F90.

```
#ifdef CESMCOUPLED
io_subsystem => shr_pio_getiosys(med_id)
pio_iotype = shr_pio_getiotype(med_id)
pio_ioformat = shr_pio_getioformat(med_id)
#else
```
The primary issue is that the med_id has to be set externally by the driver, but it is not clear in general how this should be set from a general NUOPC driver that is using CMEPS (e.g., UFS).