Container Matrix Test Engine/FeatureFlag Handling

re-check feature flag handling. we aggregate all enabled feature flags into one run - but I'm not sure if this always work correctly e.g. if:
`[2023-08-09T09:23:53.296Z] 2023-08-09 09:13:41,555 INFO : org.graylog2.featureflag.ImmutableFeatureFlagsCollector - Following feature flags are used: {default properties file=[cloud_inputs=on, search_filter=on, preflight_web=off, instant_archiving=on], environment variables=[scripting_api_preview=on]}
`

```[2023-08-09T09:23:53.296Z] 2023-08-09 09:13:42,608 INFO : org.graylog2.bootstrap.CmdLineTool - Loaded plugin: Elasticsearch 7 Support 5.2.0-SNAPSHOT+2b46f7b [org.graylog.storage.elasticsearch7.Elasticsearch7Plugin]

[2023-08-09T09:23:53.297Z] 2023-08-09 09:13:42,608 INFO : org.graylog2.bootstrap.CmdLineTool - Loaded plugin: OpenSearch 2 Support 5.2.0-SNAPSHOT+2b46f7b [org.graylog.storage.opensearch2.OpenSearch2Plugin]

[2023-08-09T09:23:53.297Z] 2023-08-09 09:13:42,697 ERROR: org.graylog2.bootstrap.CmdLineTool - Invalid configuration

[2023-08-09T09:23:53.297Z] com.github.joschi.jadconfig.ParameterException: Required parameter "instant_archiving_s3_bucket" not found.

[2023-08-09T09:23:53.297Z] at com.github.joschi.jadconfig.JadConfig.processClassFields(JadConfig.java:122) ~[graylog.jar:?]

[2023-08-09T09:23:53.297Z] at com.github.joschi.jadconfig.JadConfig.process(JadConfig.java:101) ~[graylog.jar:?]

```
config is needed for the feature flag