Merge pull request #6507 from karanvora2599/perf/videoout-unordered-cpu-flips

perf(videoout): don't hold a flip thread's CPU flips behind queued work

docs/dev/debt/libSceVideoOut.md

@@ -21,6 +21,7 @@
 - [sceVideoOutOpen](../../../core/libs/prx/libSceVideoOut/src/Output.cpp) (libSceVideoOut) - the open param's first word is unknown (PPSA21564 passes 16; it is not the byte size, since the affinity mask is at offset 16); only 16 is accepted. PPSA26344's only call at `0xCCF5EA` passes `(0xFF, 0, 0, nullptr)`. Whether a non-null param continues past offset 24 is also unknown
 - [sceVideoOutGetBufferLabelAddress](../../../core/libs/prx/libSceVideoOut/src/Buffer.cpp) exposes a port-owned contiguous array of 16 aligned 64-bit labels and returns its count. Astro Bot PPSA21564's bundled AGC driver passes a pointer output and addresses each label at `base + index * 8`. The count, zero initialization on registration, and release of the previous displayed buffer when its replacement completes follow [shadPS4](https://github.com/shadps4-emu/shadPS4/blob/23c41333822fe8eca4c609b43119180af63ae4ac/src/core/libraries/videoout/video_out.cpp) and its driver; PS5 console equivalence has not been measured. Labels live until the port closes, and reopening creates a new array. Error precedence follows the reference for null output and the existing open-port policy for handles. Exact scanout release timing, repeated same-buffer flips and concurrent guest label stores remain unverified. EOP-flip registration and interrupt tokens remain unimplemented; exposing these labels does not implement that separate API.
 - [GPU flips](../../../core/libs/prx/libSceVideoOut/src/VideoOutDriver.cpp) (libSceVideoOut) - a command-buffer flip of a buffer index with no registered buffer when the GPU reaches it presents black and completes like any flip (flip event, count, `flipPendingNum`). The console's behaviour is unknown; PPSA05684 requires that it completes: its renderer submits a flip of buffer 0 while another thread waits for `sceVideoOutIsFlipPending` to reach 0 before registering the buffers, and `flipPendingNum` counts that flip from its submission as in shadPS4
+- [sceVideoOutSubmitFlip](../../../core/libs/prx/libSceVideoOut/src/VideoOutDriver.cpp) (libSceVideoOut, libSceAgcDriver) - in the [AGC driver](../../../core/libs/prx/libSceAgcDriver/Execution/src/Driver/Queues/Submission.cpp), a CPU flip waits for the graphics-queue submissions ahead of it when the calling thread has submitted graphics-queue work itself: a title that submits a frame and flips it without waiting relies on that order, since emulated GPU work finishes later than the console's. A flip from a thread that has never submitted graphics-queue work is presented without waiting for queued submissions, unless a command-buffer or EOP flip ahead of it has not been reached. Such a thread can only know its frame is finished by waiting for it, as the PS5 RADV WSI's flip thread waits on the frame's fence. Whether the console ever orders a CPU flip behind the graphics queue is not measured; `APS5_CPU_FLIP_IN_ORDER=1` orders every CPU flip
 - [sceVideoOutAddPreVblankStartEvent](../../../core/libs/prx/libSceVideoOut/src/Event.cpp) (libSceVideoOut) - how long before the vblank the console signals pre-vblank start is unknown. The event is triggered on each emulated vblank tick immediately before the vblank event, with its own count as the event data
 - [sceVideoOutRegisterBuffers, sceVideoOutGetFlipStatus, sceVideoOutGetVblankStatus](../../../core/libs/prx/libSceVideoOut/src/Buffer.cpp) (libSceVideoOut) - PS4 callers. A handle is treated as PS4 once buffers are registered through the PS4 `sceVideoOutRegisterBuffers`; from then on its flip and vblank status are written in the PS4 64- and 32-byte layouts, with `tsc` and `submitTsc` 0. A PS4 title that reads a status before it registers buffers gets the larger PS5 layout. The PS4 function accepts only linear A8R8G8B8_SRGB (0x80000000) and A8B8G8R8_SRGB (0x80002200) buffers without options; tiled PS4 buffers throw, as their layout differs from the PS5 tiling. Linear PS4 buffers may be 4 KiB aligned: the OpenOrbis graphics sample registers its second 1920x1080 buffer 8,294,400 bytes after the first. The PS4 alignment rule is not known