Next Deliverable #2258

For the next deliverable:

• fastGPT implementation in LPython (fastGPT implementation in LPython #2409)
• Make sure LPython is at least as fast as C++ for every simple benchmark (currently we have one or two where we are slower)
• Ensure structs and pointers are rock solid, to be able to implement a simple calculator app and represent the AST in memory using structs; this will ensure that LPython can be used as a general programming language
  • Allow to initialize nested structs using "Transactions(transactions=[], accounts=[])" #2428
  • Allow to append to a list inside a struct #2429
  • Implement direct loop over list of structs #2427
• Ensure the @cpythoncall works with the LLVM backend by refactoring it into an ASR->ASR pass, similar to how the new symbolic ASR->ASR pass works: Refactor cpythoncall into an ASR pass #2470
• Allow to extend LPython with custom hardware backends #2259
• SIMD backend #2310