[Fix] (DirectVulkan, MG_State): give each transform feedback object its own capture counters

The frontend half of ARB_transform_feedback2 landed for both backends, but Magma's
capture was still written for the one implicit span GL 3.3 has:

- A paused span kept capturing. VK_EXT_transform_feedback's counter buffers already
  make consecutive draws append, so pausing is simply "do not wrap this draw" - the
  counters keep their values and the next resumed draw carries on where the last
  captured one stopped.
- Those counter buffers were context-wide. Transform feedback objects can each hold an
  open, paused span at the same time - KHR-GL40.transform_feedback.draw_xfb_test keeps
  three - and they were all appending through one set of four slots. Each object now
  gets its own group, handed out on first use; past sixteen objects they share group 0,
  which only matters for concurrently-paused spans.
- The generation that identifies a span is what a backend keys its append state on, so
  it is now part of the per-object state the frontend saves and restores. Without that,
  resuming an object that was paused before another one began looked like a new span
  and restarted its counters at zero.

GL_PRIMITIVES_GENERATED needed one more thing. It counts what the last vertex
processing stage emitted whether or not anything is being captured, but
VK_QUERY_TYPE_TRANSFORM_FEEDBACK_STREAM_EXT only counts what the capture saw - so a
draw made while the span was paused is invisible to it. The frontend now tallies those
draws, and the Vulkan query adds the delta at result time. The correction lives in the
backend that needs it: an ES driver's GL_PRIMITIVES_GENERATED counts them by itself, and
adding it there too would double them.

transform_feedback* on Magma: 4 failures -> 3. Espryt stays at 38/38.

MobileGL/MG_Backend/DirectVulkan/DirectVulkan.cpp

@@ -1578,6 +1578,12 @@ namespace MobileGL::MG_Backend::DirectVulkan {
             // (and, via the SharedPtrs, the records), never pool slots, so
             // stale queries are always safe to delete.
             Uint64 rendererGeneration = 0;
+            // Kind::XfbGenerated - the frontend's paused-draw primitive counter when the
+            // query began. VK_QUERY_TYPE_TRANSFORM_FEEDBACK_STREAM_EXT counts only what the
+            // capture saw, so a draw made while the span was paused is invisible to it -
+            // but GL_PRIMITIVES_GENERATED counts what the last vertex processing stage
+            // emitted regardless. The delta closes that gap at result time.
+            Uint64 pausedPrimitiveSnapshot = 0;
         };
     } // namespace
 
@@ -1676,6 +1682,10 @@ namespace MobileGL::MG_Backend::DirectVulkan {
                                                         primitives)) {
                 return false;
             }
+            if (query->kind == VulkanTimerQuery::Kind::XfbGenerated && MG_State::pGLContext != nullptr) {
+                primitives += MG_State::pGLContext->GetTransformFeedbackPausedPrimitiveCounter() -
+                              query->pausedPrimitiveSnapshot;
+            }
             *outNanoseconds = primitives;
             return true;
         }
@@ -1719,6 +1729,8 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         auto* query = new VulkanTimerQuery{};
         query->kind = generated ? VulkanTimerQuery::Kind::XfbGenerated : VulkanTimerQuery::Kind::XfbWritten;
         query->rendererGeneration = GetRendererGeneration();
+        query->pausedPrimitiveSnapshot =
+            MG_State::pGLContext ? MG_State::pGLContext->GetTransformFeedbackPausedPrimitiveCounter() : 0;
         return query;
     }