Enable delete via IP address

## Expected Behaviour

After provisioning and coming back later, an inlets exit-node will be known mainly by its IP rather than the internal ID used by the cloud provider.

We could do something like this for a friendlier experience:

```
inlets delete --ip 209.97.131.180
```

## Current Behaviour

We delete via an ID

```
inlets delete --id 164857028
```

## Possible Solution

if `--ip` is given, iterate and page through the instances the cloud provider has (filtered by tag?) and match on IP, then use that ID to run the deletion.

This is a follow-on feature from #1