jule: new closures

[mertcandav]

This PR implements new closures with more manually methods and high manipulation opportunities.

Featured Changes

• sema: add the Captured field to the AnonFnExprModel
• sema: analysis and collects captured variables of anonymous functions
• api: jule::Fn reimplemented

Potential Improvements / Risks

It may be possible to make further improvements regarding memory allocations for closures. Further studies on this subject may provide the necessary information for a more efficient implementation. Currently, it is guaranteed that the closure ctx allocated for each closure will be traced and released by the GC. Allocation improvements for memory mapping may be possible.

It also looks like this app doesn't have to be available for the API. In the future it may be implemented with Jule in the std::runtime package and removed from the API.