[GPU] Add log_draws: dump per-draw vertex declaration for RE

Reverse-engineering aid for decoding game mesh formats against GPU ground
truth. When the `log_draws` cvar is set, each distinct draw's primitive
type, index buffer (guest base / count / format / endianness), and full
per-stream vertex declaration (fetch-constant base + stride, and every
element's format + offset) is written to xenia_re_draws.log.

- command_processor.{h,cc}: CommandProcessor::LogDrawForRE(), no-op unless
  the cvar is set. De-dups by the vertex-declaration fingerprint (shader +
  primitive + element formats/offsets), so animated UI that redraws the
  same format into fresh buffers every frame collapses to one record --
  keeping it near-free (an earlier address-keyed de-dup flooded the log and
  stalled the GPU thread). Capped at 4096 distinct formats.
- pm4_command_processor_implement.h: call it from ExecutePacketType3Draw
  after IssueDraw (so the vertex shader has been analyzed). Backend-agnostic
  base path -- works for the Vulkan build.

Used to confirm Project Sylpheed's XBG7 mesh layout (triangle list, pos
f32x3 / normal f16x4 / uv f16x2, variable stride).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/xenia/gpu/pm4_command_processor_implement.h

@@ -1152,6 +1152,11 @@ bool COMMAND_PROCESSOR::ExecutePacketType3Draw(
                uint32_t(vgt_draw_initiator.prim_type),
                uint32_t(vgt_draw_initiator.source_select));
       }
+      // Reverse-engineering aid (no-op unless the `log_draws` cvar is set):
+      // record the guest's primitive type + index buffer + vertex declaration.
+      // Placed after IssueDraw so the vertex shader has been analyzed.
+      COMMAND_PROCESSOR::LogDrawForRE(
+          vgt_draw_initiator.value, is_indexed ? &index_buffer_info : nullptr);
     }
   }