Rysweet 4676 remove iagentruntime - collapse into iagentworker

[rysweet]

• moves AgentId into Agent
• Renames AgentRuntime to AgentMessenger (more accurate name)
• Remove IAgentRuntime Interface
• changes constructor of Agent to take IAgenWorker instead of IAgentRuntime

Why are these changes needed?

reduce code complexity and improve testability

Related issue number

closes #4676

Checks

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• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

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