"Show received messages" from Nodes (6.2+: Cluster Configuration) page

## What?

There should be a `Show received messages` link for each node on the `Nodes`/`Cluster Configuration` page, which (when clicked) initiates a search on `gl2_source_node:$NODE_ID`.

## Why?

The need is similar to the `Show received messages` option available per input on the `Inputs` page (`/system/inputs`): sometimes you want to quickly see the log messages coming in (or not coming in) through a certain path.

Having a way to directly jump from the `Nodes`/`Cluster Configuration` page to a search matching a particular node would make investigating potential node issues just a bit easier.

## Your Environment

* Graylog Version: `6.1.8`