Remove OptimizeAffineMatrix()

Reason for removal: the function does not affect performance.
The last row of the matrix is only used to compute the W component of the vector resulting from the matrix-vector multiplication.
However, since we don't actually use the W component (we shouldn't...), the compiler doesn't use the last row during the multiplication.

ScriptableRenderPipeline/HDRenderPipeline/ShaderVariables.hlsl

 float4   _FrustumPlanes[6]; // {(a, b, c) = N, d = -dot(N, P)} [L, R, T, B, N, F]
 CBUFFER_END
 
-float4x4 OptimizeAffineMatrix(float4x4 M)
-{
-    // Matrix format (x = non-constant value).
-    // | x x x x |
-    // | x x x x |
-    // | x x x x |
-    // | 0 0 0 1 |
-    // Notice that the last row is constant.
-    // We can avoid loading and doing math with constants.
-    M[3] = float4(0, 0, 0, 1);
-    return M;
-}
-
 float4x4 OptimizeProjectionMatrix(float4x4 M)
 {
     // Matrix format (x = non-constant value).

ScriptableRenderPipeline/HDRenderPipeline/ShaderVariablesMatrixDefsHDCamera.hlsl

 #ifndef UNITY_SHADER_VARIABLES_MATRIX_DEFS_HDCAMERA_INCLUDED
 #define UNITY_SHADER_VARIABLES_MATRIX_DEFS_HDCAMERA_INCLUDED
 
-#define UNITY_MATRIX_M     OptimizeAffineMatrix(unity_ObjectToWorld)
-#define UNITY_MATRIX_I_M   OptimizeAffineMatrix(unity_WorldToObject)
-#define UNITY_MATRIX_V     OptimizeAffineMatrix(_ViewMatrix)
-#define UNITY_MATRIX_I_V   OptimizeAffineMatrix(_InvViewMatrix)
+#define UNITY_MATRIX_M     unity_ObjectToWorld
+#define UNITY_MATRIX_I_M   unity_WorldToObject
+#define UNITY_MATRIX_V     _ViewMatrix
+#define UNITY_MATRIX_I_V   _InvViewMatrix
 #define UNITY_MATRIX_P     OptimizeProjectionMatrix(_ProjMatrix)
 #define UNITY_MATRIX_I_P   _InvProjMatrix
 #define UNITY_MATRIX_VP    _ViewProjMatrix

ScriptableRenderPipeline/HDRenderPipeline/ShaderVariablesMatrixDefsLegacyUnity.hlsl

 #ifndef UNITY_SHADER_VARIABLES_MATRIX_DEFS_LEGACY_UNITY_INCLUDED
 #define UNITY_SHADER_VARIABLES_MATRIX_DEFS_LEGACY_UNITY_INCLUDED
 
-#define UNITY_MATRIX_M     OptimizeAffineMatrix(unity_ObjectToWorld)
-#define UNITY_MATRIX_I_M   OptimizeAffineMatrix(unity_WorldToObject)
-#define UNITY_MATRIX_V     OptimizeAffineMatrix(unity_MatrixV)
-#define UNITY_MATRIX_I_V   OptimizeAffineMatrix(unity_MatrixInvV)
+#define UNITY_MATRIX_M     unity_ObjectToWorld
+#define UNITY_MATRIX_I_M   unity_WorldToObject
+#define UNITY_MATRIX_V     unity_MatrixV
+#define UNITY_MATRIX_I_V   unity_MatrixInvV
 #define UNITY_MATRIX_P     OptimizeProjectionMatrix(glstate_matrix_projection)
 #define UNITY_MATRIX_I_P   inverse_glstate_matrix_projection_is_not_defined
 #define UNITY_MATRIX_VP    unity_MatrixVP