UX: minor ux bugs regarding input labels that indicate how many nodes are running the input

## What?

Some minor UX bugs regarding how the Graylog UI shows how many nodes are running a particular graylog input:

* There appear to only be 2 states:
1. input is running on all nodes in a graylog cluster (green)
2. input is running on less than all nodes in graylog cluster (yellow)
* Pull based inputs that can only run on the leader node incorrectly (imo) show a yellow label that says `1 running` IMO this is confusing and should be green to indicate its health and in the expected state.
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* Stopped inputs (running on 0 nodes) is also yellow which is confusing visually. IMO these should be red.
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## Why?

Improved UX makes Graylog more accessible and easier to use and reduces confusion.

## Your Environment

* Graylog Version: 6.2.2

Please let me know if there are any questions!