Device count column on sites table

### NetBox version

v4.0.7

### Feature type

New functionality

### Proposed functionality

I would like to have a `Devices` column in the Sites table, just like we have on the Locations table.

### Use case

It would be helpful to sort the Site table to see at a glance which sites have the most devices.

### Database changes

_No response_

### External dependencies

_No response_