Remove SPU and PPU destructors

[elad335]

Enhancements

• Allow to hold smart pointers of SPU and PPU outside of IDM, need not worrying about delaying the destructors.

Bugfixes

• PPU exit syscall delayed stack memory deallocation to the destructor of PPU, causing stack to not be released for some time or not at all with detached PPU thread.
• Fix race-condition in SPU LS mapping and unmapping.

[elad335]

• SPU LS unmapping was not thread-safe as a result of a typo, fixed.

[Nekotekina]

Actually, memory_reserve should be under vm mutex too, totally forgot about it.
memory_release is fine though.

[elad335]

Done.

[Nekotekina]

Tested it a bit, freezes on close.
Noticed deallocation failure in spu_thread::cleanup another time.

rpcs3/Emu/Cell/SPUThread.cpp:1680:12: warning: unused variable ‘addr’ [-Wunused-variable]
 1680 |  const u32 addr = group ? SPU_FAKE_BASE_ADDR + SPU_LS_SIZE * (id & 0xffffff) : RAW_SPU_BASE_ADDR + RAW_SPU_OFFSET * index;
      |            ^~~~

[Nekotekina]

Seems to work now! 👍
or at least ready for testing in production