[Vulkan] Remove old Vulkan code, change shaders directory, create empty Vulkan backend

src/xenia/gpu/shaders/resolve_full_128bpp.cs.hlsl

@@ -0,0 +1,26 @@
+#include "endian.hlsli"
+#include "resolve.hlsli"
+
+RWBuffer<uint4> xe_resolve_dest : register(u0);
+ByteAddressBuffer xe_resolve_source : register(t0);
+
+[numthreads(8, 8, 1)]
+void main(uint3 xe_thread_id : SV_DispatchThreadID) {
+  // 1 thread = 2 pixels.
+  uint2 pixel_index = xe_thread_id.xy << uint2(1u, 0u);
+  // Group height is the same as resolve granularity, Y overflow check not
+  // needed.
+  [branch] if (pixel_index.x >= XeResolveSize().x) {
+    return;
+  }
+  float4 pixel_0, pixel_1;
+  XeResolveLoad2RGBAColorsX1(
+      xe_resolve_source, XeResolveColorCopySourcePixelAddressInts(pixel_index),
+      pixel_0, pixel_1);
+  // Only 32_32_32_32_FLOAT color format is 128bpp.
+  uint endian = XeResolveDestEndian128();
+  uint dest_address = XeResolveDestPixelAddress(pixel_index, 4u) >> 4u;
+  xe_resolve_dest[dest_address] = XeEndianSwap128(asuint(pixel_0), endian);
+  // Odd pixel = even pixel + 16 bytes when tiled.
+  xe_resolve_dest[dest_address + 2u] = XeEndianSwap128(asuint(pixel_1), endian);
+}