Allow copying out of the EFB copy source snapshot

When a copy with clear snapshots its source, the plain-copy path reads
the snapshot with CopyTextureToTexture, but the snapshot texture was
created without CopySrc usage.

From upstream patchzyy/Wiicompiled 6f14bde (#244, KartPad batch).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Wg7mB8ogCWmp9GH19Uc82B

aurora-main/lib/gfx/common.cpp

@@ -405,7 +405,7 @@ static size_t g_recordingSnapshotSlot = 0;
 static TextureHandle new_resolve_source_snapshot(wgpu::Extent3D size, wgpu::TextureFormat format) noexcept {
   const wgpu::TextureDescriptor textureDescriptor{
       .label = "GX Copy Source Snapshot",
-      .usage = wgpu::TextureUsage::TextureBinding | wgpu::TextureUsage::CopyDst,
+      .usage = wgpu::TextureUsage::TextureBinding | wgpu::TextureUsage::CopySrc | wgpu::TextureUsage::CopyDst,
       .dimension = wgpu::TextureDimension::e2D,
       .size = size,
       .format = format,