Default inputs to global

## What?

If people are running Graylog in the manner we recommend, anytime they have a cluster it should be behind a load balancer, so inputs then need to be global all the time.

## Why?

I could not tell you the last time I directed someone to make a local input only, however I'm sure it's confusing for new people when making an input, name is self explanatory but the global input option is the only other option that you really need to change when making a new input unless you need to do anything special.

## Your Environment

* Graylog Version:
* OpenSearch Version:
* MongoDB Version:
* Operating System:
* Browser version: