[type-asserts] Move checker (merge_js) from Ty_visitor to ppx_visitors
[type-asserts] Move checker (merge_js) from Ty_visitor to ppx_visitors

Reviewed By: samwgoldman

Differential Revision: D9501035

fbshipit-source-id: 399519397c68ac1294827f39de9f9267eafdd0fd

popham/flow,samwgoldman/flow,nmote/flow,AgentME/flow,gabelevi/flow,facebook/flow,samwgoldman/flow,mroch/flow,samwgoldman/flow,popham/flow,popham/flow,samwgoldman/flow,jamesgpearce/flow,popham/flow,mroch/flow,facebook/flow,mroch/flow,jamesgpearce/flow,AgentME/flow,nmote/flow,jamesgpearce/flow,JonathanUsername/flow,jamesgpearce/flow,nmote/flow,nmote/flow,JonathanUsername/flow,mroch/flow,samwgoldman/flow,AgentME/flow,jamesgpearce/flow,gabelevi/flow,popham/flow,mroch/flow,gabelevi/flow,gabelevi/flow,JonathanUsername/flow,JonathanUsername/flow,popham/flow,JonathanUsername/flow,jamesgpearce/flow,facebook/flow,mroch/flow,facebook/flow,JonathanUsername/flow,samwgoldman/flow,AgentME/flow,nmote/flow,nmote/flow,facebook/flow,mroch/flow,gabelevi/flow,AgentME/flow,popham/flow,jamesgpearce/flow,gabelevi/flow,facebook/flow,samwgoldman/flow,gabelevi/flow,JonathanUsername/flow,nmote/flow,facebook/flow