Add `catch_body` to baseline mapper
Add `catch_body` to baseline mapper

Summary: This adds a `catch_body` method to the Flow_mapper class which will be called when mapping through a `try-catch`.

Reviewed By: arcanis

Differential Revision: D13040144

fbshipit-source-id: b033b781e728cbf30b2bb0777c073e78ec86fca0

mroch/flow,samwgoldman/flow,AgentME/flow,samwgoldman/flow,gabelevi/flow,popham/flow,gabelevi/flow,AgentME/flow,popham/flow,gabelevi/flow,AgentME/flow,facebook/flow,samwgoldman/flow,facebook/flow,facebook/flow,gabelevi/flow,mroch/flow,gabelevi/flow,mroch/flow,samwgoldman/flow,popham/flow,popham/flow,mroch/flow,samwgoldman/flow,gabelevi/flow,mroch/flow,mroch/flow,facebook/flow,samwgoldman/flow,samwgoldman/flow,AgentME/flow,gabelevi/flow,mroch/flow,popham/flow,popham/flow,AgentME/flow,facebook/flow,facebook/flow,popham/flow,facebook/flow