Reactor: Switch swizzles over to 16-bit hex codes

This migrates from 2-bit swizzle codes per lane to 4-bit, which reads more fluently in hex.
The order has been reversed so that the most significant nibble (leftmost on little-endian CPUs) represents the first output lane.

Fixed up Swizzle, Mask, and ShuffleLowHigh

Bug: b/145746360
Change-Id: I132bd757801a5ca543ef2b9b0ed34d0527db5bfa
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/39049
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: David Turner <digit@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Ben Clayton <bclayton@google.com>

src/Renderer/QuadRasterizer.cpp

diff --git a/src/Renderer/QuadRasterizer.cpp b/src/Renderer/QuadRasterizer.cpp
index 947a88b..a16c457 100644
--- a/src/Renderer/QuadRasterizer.cpp
+++ b/src/Renderer/QuadRasterizer.cpp
@@ -272,8 +272,8 @@
 					xLeft[q] = *Pointer<Short4>(primitive + q * sizeof(Primitive) + OFFSET(Primitive,outline) + y * sizeof(Primitive::Span));
 					xRight[q] = xLeft[q];
 
-					xLeft[q] = Swizzle(xLeft[q], 0xA0) - Short4(1, 2, 1, 2);
-					xRight[q] = Swizzle(xRight[q], 0xF5) - Short4(0, 1, 0, 1);
+					xLeft[q] = Swizzle(xLeft[q], 0x0022) - Short4(1, 2, 1, 2);
+					xRight[q] = Swizzle(xRight[q], 0x1133) - Short4(0, 1, 0, 1);
 				}
 
 				For(Int x = x0, x < x1, x += 2)