Implement filter config for generate-filter

[bastianjoel]

It should be possible to pass a configuration file to generate-filter which contains:

• Excluded collections
• Excluded field names
• Field names which specify additional fields and are not searchable (making https://github.com/OpenSlides/openslides-search-service/blob/main/cmd/generate-filter/main.go#L64 unnecessary)
• Per collection excluded fields

[bastianjoel]

We should discuss if it makes sense to keep maintaining the auto generation of the search.yml as it seems to be more efficient to maintain the config manually.