[[inputs.icinga2]] - Services object query - specify specfic host and service

Hello,

It looks like this plugin doesn’t query all services objects including hosts and their services. Is there a way to make it happen? Thanks

e.g. https://testicinga.com:5665/v1/objects/services/host-name!icinga

```
[[inputs.icinga2]]
## Required Icinga2 server address
server = "https://testicinga.com:5665"

## Collected Icinga2 objects ("services", "hosts")
## Specify at least one object to collect from /v1/objects endpoint.
# objects = ["services"]
objects = ["services", "hosts"]

## Collect metrics from /v1/status endpoint
## Choose from:
## "ApiListener", "CIB", "IdoMysqlConnection", "IdoPgsqlConnection"
# status = []
status = ["ApiListener", "CIB", "IdoMysqlConnection"]

## Credentials for basic HTTP authentication
username = "user"
password = "pass"
```

Start with the inputs.icinga2 plugin and its handling of the Icinga2 /v1/objects endpoint. Reproduce the request using the example services/host-name!icinga path, then determine how the objects setting should support querying a specific host and service; done means the requested services are returned without breaking the existing hosts and services queries.

Written by the indexing model from the issue text.