[Feat] (MG_Impl, MG_State, MG_Util): attach a buffer texture to a range of its buffer

glTexBufferRange, glTextureBuffer and glTextureBufferRange were all stubs, so a
buffer texture could only ever be attached through glTexBuffer -- by binding, and
always to the whole buffer.

Give the buffer texture the window it is supposed to address. The non-range forms
record it as offset 0 with a whole-buffer sentinel rather than the size the buffer
happens to have, so a later respecify keeps being followed instead of freezing the
texture at yesterday's size. All four entry points now share one attach path,
differing only in how they name the texture: by binding for the target forms, by
name for the DSA ones.

Both backends honour the window: DirectVulkan offsets and clamps the buffer view,
DirectGLES uses glTexBufferRange when the texture names a sub-range and keeps
plain glTexBuffer for the whole-buffer case, which also works on a driver without
the range entry point.

GL_TEXTURE_BUFFER_OFFSET_ALIGNMENT reported 0 with a comment explaining that the
range entry points were stubbed. It now reports what the device actually requires
-- minTexelBufferOffsetAlignment on Vulkan, the driver's own value on GLES -- and
the range entry points enforce it. Zero was never a legal answer; the minimum is
1, and an application that trusted it would have built unaligned offsets.

MobileGL/MG_Backend/DirectVulkan/Renderer/UniformManager.cpp

@@ -600,7 +600,11 @@ namespace MobileGL::MG_Backend::DirectVulkan {
 
         const VkDeviceSize texelSize =
             static_cast<VkDeviceSize>(MG_Util::GetSizedInternalFormatSizeInBytes(internalFormat));
-        VkDeviceSize viewRange = slice.size;
+        // glTextureBufferRange addresses a window of the buffer, not all of it; the whole-buffer
+        // forms report the buffer's current size here, so both go through the same clamp.
+        const VkDeviceSize rangeOffset = static_cast<VkDeviceSize>(textureBuffer->GetBufferRangeOffset());
+        const VkDeviceSize rangeSize = static_cast<VkDeviceSize>(textureBuffer->GetBufferRangeSizeInBytes());
+        VkDeviceSize viewRange = std::min(rangeSize, slice.size > rangeOffset ? slice.size - rangeOffset : 0);
         if (texelSize > 0) {
             viewRange = (viewRange / texelSize) * texelSize;
         }
@@ -613,7 +617,7 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         viewInfo.sType = VK_STRUCTURE_TYPE_BUFFER_VIEW_CREATE_INFO;
         viewInfo.buffer = slice.buffer;
         viewInfo.format = vkFormat;
-        viewInfo.offset = slice.offset;
+        viewInfo.offset = slice.offset + rangeOffset;
         viewInfo.range = viewRange;
 
         VkBufferView bufferView = VK_NULL_HANDLE;