Skip conditional rendering prep when nothing can consume it

The Qualcomm driver does not expose VK_EXT_conditional_rendering, which is why
the vendor gate added earlier never fired: the feature was already off, so
turning it off changed nothing.

But VKGSRender::begin_conditional_rendering does its work regardless of support.
It allocates the predicate buffer, copies query results into it and barriers it,
then falls through to the base implementation. Only vkCmdBeginConditionalRendering
reads that buffer, so without the extension all of it is discarded.

On Adreno the waste is not merely wasted. insert_buffer_memory_barrier ends the
open render pass, and that driver allocates on every vkCmdEndRenderPass and does
not release it. A heap profile of a Skate 3 session put its largest allocation
stacks, 157MB, 152MB, 150MB and more, on exactly this path through
qglinternal::vkCmdEndRenderPass into calloc, with the process killed at 4.3GB of
anonymous memory after about 2.4GB arrived in eight seconds.

Returns to the base implementation immediately when the extension is missing.
Behaviour is unchanged, since nothing was being predicated anyway; what goes is
the buffer traffic, the barriers and the render pass ends.

rpcs3/Emu/RSX/VK/VKGSRender.cpp

@@ -2904,6 +2904,27 @@ void VKGSRender::begin_conditional_rendering(const std::vector<rsx::reports::occ
 {
 	ensure(!sources.empty());
 
+	// Without the extension there is nothing that can read the predicate, so building it is
+	// pure cost.
+	//
+	// The aggregation below fills m_cond_render_buffer and only vkCmdBeginConditionalRendering
+	// consumes it. Where VK_EXT_conditional_rendering is absent the buffer is written, barriered
+	// and then dropped, and the code falls through to the base implementation regardless.
+	//
+	// On Adreno that waste is not merely wasted. Each insert_buffer_memory_barrier ends the
+	// open render pass, and that driver allocates on every vkCmdEndRenderPass without
+	// releasing it. A heap profile of a Skate 3 session put its largest allocation stacks,
+	// 157MB, 152MB, 150MB and more, on exactly this path through
+	// qglinternal::vkCmdEndRenderPass into calloc, and the process was killed at 4.3GB.
+	//
+	// The Qualcomm driver does not expose the extension at all, so this path could never
+	// have predicated anything there.
+	if (!m_device->get_conditional_render_support())
+	{
+		rsx::thread::begin_conditional_rendering(sources);
+		return;
+	}
+
 	// Flag check whether to calculate all entries or only one
 	bool partial_eval;