Refactor RO backend data structures (#49)

- Remove hdp and ipc pointers from BlockHandle, align RO stats with RO contexts

- Add run commands for `rocshmem_g` and `rocshmem_p` API tests in driver.sh

- Allocate rocshmem API return buffers based on number of device contexts.

- Associate status flag address with blocking calls and remove threadId dependency
   - Associated the status flag address with each blocking call request to notify the GPU thread.
   - Removed dependency on threadId for determining the appropriate status flag index.

- Move status flag buffer allocation to backend.

- Initialize allocated memeory to zero

src/reverse_offload/backend_proxy.hpp

@@ -36,10 +36,8 @@ struct BackendRegister {
   std::atomic<bool> worker_thread_exit{false};
   bool *needs_quiet{nullptr};
   bool *needs_blocking{nullptr};
-  char *g_ret{nullptr};
   HdpPolicy *hdp_policy{nullptr};
   WindowInfo **heap_window_info{nullptr};
-  atomic_ret_t *atomic_ret{nullptr};
   SymmetricHeap *heap_ptr{nullptr};
 };