Align and merge integration types #399
Description
We have some types of integrations that are unique but I suggest we should merge them with another type.
For example, HanLP is of type Preprocessor and the only integration of that type: https://haystack.deepset.ai/integrations?type=Preprocessor
We could merge it into Data Ingestion, which contains 11 integrations.
Similarly, Data Integration and Converter each contain only one integration and we could merge them into the type Data Ingestion too.
I am not sure what to do with Search & Extraction. Merge it into Data Ingestion too or make sure that other Web Search integration are moved to Search & Extraction, for example DuckDuckGo or Trafilatura.
I wonder if we should add integration pages for SerperDev and SearchAPI given that Haystack works with them too but the functionality is part of Haystack core at the moment: https://docs.haystack.deepset.ai/docs/websearch Could be a separate issue?