vine: library functions in remote execution cannot be composed

[btovar]

This issue came up in #4011. Say a user defines a library with function fn and wants to use it in a map. The auxiliary function for chunks in map would also need to run remotely, which means that either it should be added to the library, or be included in the library support code from poncho. When running library functions, their arguments are wrapped in an event json rpc, thus it becomes difficult to compose them.

One solution would be to make the auxiliary functions understand the json rpcs, but that would make further changes to code difficult. Another option is to modify the @remote_execution decorator so that by default it calls the original function, and only calls the version with the rpc json arguments when called like fn.wrapped. With this, only the top call in library_code would use fn.wrapped.

[btovar]

It is likely that this shares the same underlying issue as #4040