* Refactor group chat workflow to prevent message echoing and enhance checkpointing
- Updated GroupChatWorkflowBuilder to disable forwarding incoming messages to prevent duplicates.
- Enhanced RoundRobinGroupChatManager with checkpointing support to preserve state across executions.
- Modified GroupChatHost to maintain a history of messages and track the current speaker for message broadcasting.
- Implemented broadcasting logic to ensure participants receive messages from others while excluding their own responses.
- Added comprehensive unit tests for group chat orchestration, including scenarios for tool approval and function calls.
- Introduced a new ApprovalHarness for testing tool invocation and approval workflows.
* fixup: format
* Add JSON serialization support for GroupChatManagerState and RoundRobinGroupChatManagerState
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Co-authored-by: Jacob Alber <jalber@lokitoth.com>
* refactor: remove unused internals
* feat: Execution Mode for sharing a workflow among concurrent runs
* feat: Update WorkflowHostAgent to support concurrent execution
* Also update AsAgent APIs to support injecting a CheckpointManager and an IWorkflowExecutionEnvironment
* fix: Make Read logic consistent in DeclarativeWorkflowContext
