Add Packetbeat default configuration file to Sidecar defaults

## What?

- With the other "beats" supported, Graylog provides default configuration files for use with Sidecar. Now that we have added Packetbeat support, we want to provide an out of the box packetbeat sidecar config for our customers to use in conjunction with our content pack.

## Why?

- Users will be able to easily initialize/deploy packetbeat via sidecar without manual config file editing.

## Additional Details
- I have already finished and tested the config, it is currently running in my environment, and I am dropping it here as well.

[packetbeat-sidecar-config.json](https://github.com/Graylog2/graylog2-server/files/15437317/packetbeat-sidecar-config.json)