Ketan simplified co act workflow

[ketan1741]

Short description of the problem this fixes or functionality that this introduces. This may be used for the CHANGELOG

• This PR implements a simplified multi-agent workflow inspired by the CoAct paper.
• Currently, in swe-bench eval, there are complex instances that OpenHands fails, especially ones that single CodeActAgent overlooks the buggy location. If we have a grounding test case for the issue, this workflow seems to help.
• An overkill-ish successful trajectory with replanning can be found here.
• A task which CoActPlannerAgent finished but CodeActAgent failed (I expected both to be able to complete it):
  CoAct traj
  CodeAct traj

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Give a summary of what the PR does, explaining any non-trivial design decisions

• Modify CodeAct to make it accept delegated task.
• Implement 2 new agents, planner and executor with the same abilities as CodeAct, different system prompts, additional action parsers.

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Link of any specific issues this addresses

[neubig]

Hey @ketan1741 , I'm confused. How does this relate to #3770 ?

[ketan1741]

Hey @ketan1741 , I'm confused. How does this relate to #3770 ?

Hey, Prof. @neubig! Hoang wanted me to have a different branch if I were to make updates to our workflow implementation to make it more reliable/improve it.

[neubig]

Ah, I see. We can figure this out.