.NET: [Feature]: Implement sample to demonstrate Foundry Toolbox integration and invocation from Declarative workflows

### Description

sample to demonstrate how to embed and invoke Foundry Toolbox in declarative workflows and how to wire that up to an agent conversation. This allows for more tool types to be invoked directly in declarative workflow nodes beyond the explicitly supported tools (HttpRequest, FunctionTool and MCPTool).

### Code Sample

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### Language/SDK

.NET