[HAProxy]: Add hostname control to dashboards

### Integration Name

HAProxy [haproxy]

### Dataset Name

haproxy.stat

### Integration Version

1.17.2

### Agent Version

8.19

### OS Version and Architecture

Debian Bookworm x86_64

### User Goal

Get an overview of our HAProxy clusters but also be able to "zoom in" on specific node(s). It should be possible to quickly filter for one or more hostnames (default: ALL).

### Existing Features

The current dashboards appear to be an aggregation of existing metrics over all hosts. This does not allow to (e.g. monitor) specific nodes or clusters by simply selecting them. Only way is to enter search queries all the time.

Adding a hostname filter requires duplications the dashboards to be able to add a hostname control and because of this having to closely monitor if dashboard change with each and every integration update to adjust the clones as well. (This is a very common issue with the Dashboards provided by Elastic integrations.)

### What did you see?

Which cluster? Which node? (-> ALL of them combined?)

### Anything else?

Maybe you could add the default search query (e.g. `haproxy.stat.component_type : 0`) as a filter (like the filter for the dataset)