[Feat] Create a delegate to agent tool

[abhipatel12]

As we add the ability to configure more subagents via custom configs and extensions, we should take the opportunity to reduce the impact of the increase in tool registrations.

Instead of a 1-to-1 b/w tool and subagent, this architecture instead supports 1-to-many (single tool for many subagents)

This new tool will take the following params:

• Agent Name
• Input Prompt

This allows for a single tool to access multiple agents. The tool definition will contain the list of the available subagents.

Completion criteria:

• [ ] Create a new tool that is used to delegate to registered subagents
• [ ] Validate that ability to call subagents is not diminished due to this pattern