Add visualization of Agent Message Transitions State in AGS

[victordibia]

Add the ability to visualize control flow messages sent by agents. Each message has a source, in the AgentChat. The visualization shows

• messages being sent
• draws a line (which should be interpreted as a transition) between the agent that sent the previous message and the current agent. This is not direct message sending (agentchat is event driven), rather, a message was sent, delivered by the runtime to the next agent which sents the next message.

Why are these changes needed?

Related issue number

Closes #4067

Checks

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