With Cloud Sync in automatic mode, closing content asks for a sync.
When content is running, CMD_EVENT_UNLOAD_CORE now only marks it
(RARCH_FLAGS_CLOUD_SYNC_ON_DEINIT), and retroarch_main_deinit_finish
pushes it: by then the content's save RAM has been flushed and no
core owns the save file, so the sync uploads and hashes the save the
content left behind, and may update it from the server. With no
content running the sync is pushed at once, as before. On the way out
the task queue has already been drained, so a sync marked there is
dropped, as one pushed before the drain was cancelled.
samples/runloop/cloudsync_unload links the shipping retroarch.c with
task_push_cloud_sync wrapped, loads a core with save RAM, closes the
content from a frame loop and checks what the save file held when the
sync was asked for. It runs in the menu harness workflow.
