`api list` to `api get`

**Is your feature request related to a problem? Please describe.**
Currently, `aio rt api list` requires a base path of the api to return results. The behavior of the `list` command is inconsistant with other `list`s (like `action list`). We think `get` may be the better verb here as all other `get`s do expect arg to return results.

```
aio rt api list --help
list route/apis for Adobe I/O Runtime

USAGE
$ aio runtime:route:list [BASEPATH] [RELPATH] [APIVERB]

ARGUMENTS
BASEPATH The base path of the api
RELPATH The path of the api relative to the base path
APIVERB (get|post|put|patch|delete|head|options) The http verb
```

**Describe the solution you'd like**
Instead of `api list`, change the default to `api get` and retain `list` as an alias for openwhisk users

**Additional context**
related to https://github.com/adobe/aio-cli-plugin-runtime/issues/184