[ABI] Implement Windows ABI for x86_64
Implement the ABI for WIndows-x86_64 including register info and calling convention.
Handled nested struct returned in register (SysV doesn't have it supported)
Reviewers: xiaobai, compnerd
Reviewed By: compnerd
Subscribers: labath, jasonmolenda, fedor.sergeev, mgorny, teemperor, lldb-commits
Differential Revision: https://reviews.llvm.org/D62213