add fill for selected tools

[xinyual]

Description

We want to use a MLModelTool to firstly do tool selection and then limit the tool root agent can use. It will improve the tool selection accuracy. To do so, we need to fill the "TOOL_SELECT" field by previous MLMODELTool's output.

The request body would be like:

{
  "name": "Test_Agent_For_RAG_2",
  "type": "flow",
  "description": "Use this tool to transfer natural language to generate PPL and execute PPL to query inside. This tool will select index by itself. The input parameters are: {'question':UserQuestion}",
  "memory": {
    "type": "demo"
  },
  "tools": [
    {
      "type": "MLModelTool",
      "name": "RepCToolSelection",
      "description": "repc",
      "parameters": {
        "model_id": "<repc_id>",
        "prompt": "${parameters.question}"
      }
    },
      {
      "type": "AgentTool",
      "name": "RootAgent",
      "description": "root agent with all tools",
      "parameters": {
        "agent_id": "<root_agent_id>",
        "selected_tools": "[\"${parameters.RepCToolSelection.output}\"]"
      }
    }
  ]
}

Issues Resolved

[List any issues this PR will resolve]

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff

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[codecov]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (5cba422) 81.87% compared to head (e819e30) 81.85%.
Report is 1 commits behind head on main.

Files	Patch %	Lines
...nsearch/ml/engine/algorithms/agent/AgentUtils.java	16.66%	4 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2150      +/-   ##
============================================
- Coverage     81.87%   81.85%   -0.02%     
- Complexity     5662     5663       +1     
============================================
  Files           543      543              
  Lines         22857    22864       +7     
  Branches       2350     2350              
============================================
+ Hits          18714    18716       +2     
- Misses         3203     3207       +4     
- Partials        940      941       +1     

Flag	Coverage Δ
ml-commons	81.85% <28.57%> (-0.02%)	⬇️

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