Use target independent builtins

Created by: adeel10x

This PR is not ready for the merge because I haven't covered all possible corev bitmanip builtins yet. For now, only the __builtin_riscv_cv_bitmanip_ror has been replaced with the target independent __builtin_rotateright32. I am creating a PR so that concerned developers can review the code that has been pushed so far and provide their valuable feedback.