[Fix] (DirectVulkan): raw sRGB attachment writes while FRAMEBUFFER_SRGB is off

GL renders into sRGB color attachments RAW when GL_FRAMEBUFFER_SRGB is
disabled (the core-profile default), but Vulkan sRGB attachments always
encode on write - one decode went missing whenever a rendered-into sRGB
texture was sampled again (multisampled sRGB targets in
texture_size_promotion and texture_swizzle idx27/28 ms cases).

Attachment views (textures and renderbuffers) now reinterpret sRGB
images through their UNORM twin while the capability is off, switching
back when enabled: images get MUTABLE_FORMAT, the attachment-view cache
keys the view format, renderbuffers carry a second view, and the render
pass hash includes the capability state. Sampled views keep decoding.
The VkTextureManager.cpp half of this rides with the next commit.

MobileGL/MG_Backend/DirectVulkan/Renderer/VkRenderPassManager.h

@@ -274,6 +274,9 @@ namespace MobileGL::MG_Backend::DirectVulkan {
             VkImage image = VK_NULL_HANDLE;
             VmaAllocation allocation = nullptr;
             VkImageView view = VK_NULL_HANDLE;
+            // UNORM reinterpretation of an sRGB image, used as the attachment view while
+            // GL_FRAMEBUFFER_SRGB is disabled (raw writes). Null for non-sRGB formats.
+            VkImageView unormTwinView = VK_NULL_HANDLE;
             VkImageLayout layout = VK_IMAGE_LAYOUT_UNDEFINED;
             VkFormat format = VK_FORMAT_UNDEFINED;
             VkImageAspectFlags aspect = VK_IMAGE_ASPECT_NONE;
@@ -307,6 +310,7 @@ namespace MobileGL::MG_Backend::DirectVulkan {
             VkImage image = VK_NULL_HANDLE;
             VmaAllocation allocation = nullptr;
             VkImageView view = VK_NULL_HANDLE;
+            VkImageView unormTwinView = VK_NULL_HANDLE;
             Uint64 deferredAtFrame = 0;
         };