[vk, renderdoc] fixed zero-sized streambuffer bug on old heap-absent GPUs (#4052)

This fix a bug in which eden crashes when renderdoc is attached to vulkan.
that kept me away from renderdoc for around a year now.

the bug:

in video_core\renderer_vulkan\vk_staging_buffer_pool.cpp
in GetStreamBufferSize(...)
if device.HasDebuggingToolAttached()
but heap is empty/unavailable <-- Case in my old nvidia kepler gpu

the original method returns size 0, right?
the change honors same original behavior, while covers my case properly, returning MAX_STREAM_BUFFER_SIZE.

addl some log tip and some minimal doc. fully safe. let it rip.

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/4052
Reviewed-by: MaranBr <maranbr@eden-emu.dev>
Reviewed-by: Lizzie <lizzie@eden-emu.dev>

docs/Debug.md

@@ -69,29 +69,6 @@ Expressions can be `variable_names` or `1234` (numbers) or `*var` (dereference o
 
 For more information type `info gdb` and read [the man page](https://man7.org/linux/man-pages/man1/gdb.1.html).
 
-## Simple checklist for debugging black screens using Renderdoc
+# RenderDoc (Graphic Debugging Tool)
 
-Renderdoc is a free, cross platform, multi-graphics API debugger. It is an invaluable tool for diagnosing issues with graphics applications, and includes support for Vulkan. Get it at [renderdoc.org](https://renderdoc.org).
-
-Before using renderdoc to diagnose issues, it is always good to make sure there are no validation errors. Any errors means the behavior of the application is undefined. That said, renderdoc can help debug validation errors if you do have them.
-
-When debugging a black screen, there are many ways the application could have setup Vulkan wrong.
-Here is a short checklist of items to look at to make sure are appropriate:
-
-- Draw call counts are correct (aka not zero, or if rendering many triangles, not 3)
-- Vertex buffers are bound
-- vertex attributes are correct - Make sure the size & offset of each attribute matches what should it should be
-- Any bound push constants and descriptors have the right data - including:
-  - Matrices have correct values - double check the model, view, & projection matrices are uploaded correctly
-- Pipeline state is correct
-  - viewport range is correct - x,y are 0,0; width & height are screen dimensions, minDepth is 0, maxDepth is 1, NDCDepthRange is 0,1
-  - Fill mode matches expected - usually solid
-  - Culling mode makes sense - commonly back or none
-  - The winding direction is correct - typically CCW (counter clockwise)
-  - Scissor region is correct - usually same as viewport's x,y,width, &height
-- Blend state is correct
-- Depth state is correct - typically enabled with Function set to Less than or Equal
-- Swapchain images are bound when rendering to the swapchain
-- Image being rendered to is the same as the one being presented when rendering to the swapchain
-
-Alternatively, a [RenderDoc Extension](https://github.com/baldurk/renderdoc-contrib/tree/main/baldurk/whereismydraw) ([Archive](https://web.archive.org/web/20250000000000*/https://github.com/baldurk/renderdoc-contrib/tree/main/baldurk/whereismydraw)) exists which automates doing a lot of these manual steps.
+Guidelines for graphical debugging using RenderDoc: **[RenderDoc usage](./RenderDoc.md)**