[Feature Request]: new high-level programming interface

[sonichi]

Is your feature request related to a problem? Please describe.

Offer a simpler high-level programming interface for common orchestration patterns such as Swarm-style handsoff.
Extend it to incorporate group chat, nested chat and sequential chats.
Offer builtin tools that an agent can register for these common chat patterns.
Enable self-execution for swarm-style agents.

Describe the solution you'd like

from autogen import SwarmAgent, autobuild_groupchat, initiate_chat

captain = SwarmAgent("captain", llm_config=..., human_input_mode="NEVER")
user_proxy = SwarmAgent("user_proxy")
planner = SwarmAgent("planner", llm_config=..., human_input_mode="NEVER")
team_creator = SwarmAgent("team_creator", llm_config=..., human_input_mode="NEVER", functions=[autobuild_groupchat])

user_proxy.register_handoff(hand_to=captain)  # always hand off to captain after human input
captain.register_handoff(
    hand_to=[
        ON_CONDITION(nested_chat=[chat_with_planner, chat_with_team_creator, ...], condition="You need help from a planner. The user does not need to be involved in the planning."),
        ON_CONDITION(agent=planner, condition="You need help from a planner. The user would like to be involved in the planning"),
        ON_CONDITION(agent=team_creator, condition="The plan has been generated. A team is needed to execute the next step in the plan.")
        AFTER_WORK(user_proxy),  # After work, choose user proxy
    ]
)
planner.register_handoff(
    hand_to=[
        AFTER_WORK("If the user would like to be involved in the planning and has't approved the latest plan, hand off to user proxy. Otherwise handoff to captain."),
    ]
)
team_creator.register_handoff(hand_to=[AFTER_WORK(captain)])

initiate_chat(sender=captain, message="How can I help you?")  # a default group chat is created automatically when omitted

Benefits:

1. Simplify user's code in tool use, group chat, nested chat etc. They are handled by the library automatically.
2. Offer built-in tools like autobuild_groupchat.
3. Can still leverage all the conversation patterns we support and expand the ways to use them.
4. Compatible with swarm-style handsoff.

Note:
Only one AFTER_WORK is allowed. Multiple ON_CONDITION is allowed.
ON_CONDITION corresponds to tool-based handoff.
AFTER_WORK corresponds to speaker selection after the work of the agent is done and no other agent is selected by a tool call. It can be both NL-based selection or PL-based.

Additional context

Will create a task list to break down the implementation plan.

[marklysze]

With Nested Chat, #107, complete and merged. Will close this. Swarm will continue to develop with additional features and these can be created in a new Issue.