cellSpursAddUrgentCommand searches in 4 slots for an empty slot to put the command at.
At first, it seems to do so unordered.
Meanwhile, on SPU side, it expects an order between all the commands because it pops them it in FIFO manner.
Not keeping track of how many commands are queued in total.
After second observation of cellSpursAddUrgentCommand, something odd comes takes places here.
Usually, reservation loops are individual and are expected to be closed without any changes of the previous loop affected by the proceeding one.
But in this case, after a single failure, the entire operayion is reset, a loop of 4 reservation operations suddenly is reset completely.
This makes one wonder if it the HW expects sometjing else here, perhaps it caches the reservation internally here?
After some adjustments to LDARX and STDCX to cache the reservation between succeeding loops, Metal Gear Solid 4 no longer freezes!
Replaces `std::shared_pointer` with `stx::atomic_ptr` and `stx::shared_ptr`.
Notes to programmers:
* This pr kills the use of `dynamic_cast`, `std::dynamic_pointer_cast` and `std::weak_ptr` on IDM objects, possible replacement is to save the object ID on the base object, then use idm::check/get_unlocked to the destination type via the saved ID which may be null. Null pointer check is how you can tell type mismatch (as dynamic cast) or object destruction (as weak_ptr locking).
* Double-inheritance on IDM objects should be used with care, `stx::shared_ptr` does not support constant-evaluated pointer offsetting to parent/child type.
* `idm::check/get_unlocked` can now be used anywhere.
Misc fixes:
* Fixes some segfaults with RPCN with interaction with IDM.
* Fix deadlocks in access violation handler due locking recursion.
* Fixes race condition in process exit-spawn on memory containers read.
* Fix bug that theoretically can prevent RPCS3 from booting - fix `id_manager::typeinfo` comparison to compare members instead of `memcmp` which can fail spuriously on padding bytes.
* Ensure all IDM inherited types of base, either has `id_base` or `id_type` defined locally, this allows to make getters such as `idm::get_unlocked<lv2_socket, lv2_socket_raw>()` which were broken before. (requires save-states invalidation)
* Removes broken operator[] overload of `stx::shared_ptr` and `stx::single_ptr` for non-array types.
