Allow field highlight feature to highlight a different field than the one used to create the rule

## What?

Allow field highlight feature to highlight a different field than the one used to create the rule

## Why?

Currently, you can highlight a field by matching a value in that field. However, there may be data in the log message that you want to use for highlighting criteria, but to actually highlight a different field. This would be very useful where you might want the message text to be red when the level is error. While you can have the word error highlighted red, it would be nice to not have to have the column in the table solely because you need it to see the highlighted color.

## Your Environment

* Graylog Version: 5.1.3
* OpenSearch Version: 2.8.0
* MongoDB Version: 6.0.7
* Operating System: Ubuntu Server 22.04 LTS
* Browser version: Google Chrome Version 114.0.5735.198 (Official Build) (arm64)