[Feat] (DirectVulkan): combined and scissored blits; cross-format depth-stencil blits

BlitFramebuffer now serves any GL_COLOR/DEPTH/STENCIL mask combination:
the depth/stencil aspects run as per-aspect image copies before the color
path, renderbuffer attachments materialize their pending clears like
texture ones, and the scissor test clips blit writes (destination rect
intersected, source shrunk proportionally). Depth copies between images
of different depth formats (a D24S8 renderbuffer into a
DEPTH_COMPONENT24 texture riding the D32_SFLOAT fallback) round-trip
through the host with a per-texel re-encode; stencil aspects pass
through raw since every packed format encodes S8. scissor_blit and
packed_depth_stencil.blit.* now pass.

MobileGL/MG_Backend/DirectVulkan/Renderer/VulkanRenderer.h

@@ -211,6 +211,14 @@ namespace MobileGL::MG_Backend::DirectVulkan {
                                            VkImageAspectFlags imageAspect, Uint32 mipLevel, Uint32 baseArrayLayer,
                                            GLint x, GLint y, GLsizei width, GLsizei height, GLenum format, GLenum type,
                                            void* pixels);
+        // Same-extent depth blit between images of different depth formats: host
+        // round-trip with a per-texel re-encode (see BlitNamedFramebuffer).
+        Bool BlitDepthAcrossFormats(FrameContext::FrameData& frame, VkImage srcImage, VkFormat srcFormat,
+                                    VkImageLayout* srcTrackedLayout, Uint32 srcMipLevel, Uint32 srcBaseArrayLayer,
+                                    VkImage dstImage, VkFormat dstFormat, VkImageLayout* dstTrackedLayout,
+                                    Uint32 dstMipLevel, Uint32 dstBaseArrayLayer, GLint srcX, GLint srcY, GLint dstX,
+                                    GLint dstY, GLint width, GLint height, VkImageLayout srcRestoreLayout,
+                                    VkImageLayout dstRestoreLayout, Bool stencilAspect);
         static SizeT GetReadbackTexelSize(VkFormat sourceFormat);
         static Bool ConvertReadbackPixels(const Uint8* sourcePixels, VkFormat sourceFormat,
                                           GLsizei width, GLsizei height, GLenum destinationFormat,