Add tool to use a pipeline for search

[mathislucka]

Overview
See REPO.md for general contribution guidelines.

We want to add a tool and MCP tool for using a pipeline for search. The search functionality is already implemented in the PipelineResource, we just need to add it as tool and mcp tool.

Requirements

• the search tool should only allow to pass in a query, we do not support any other features (filters, additional params etc)
• the search response should be brought into an llm readable format (convert it to a string - similar to other string conversions for other tools)
• inside the tool, we should check for pipeline deployment status, if the pipeline is not deployed, we do not execute the search and return a string telling the llm to deploy the pipeline first
• all errors are converted to strings
• add unit tests for the tool (same approach as for other tools)