LibGL: Turn Sampler2D into an actual class

This extracts the sampler functionality into its own class.
Beginning with OpenGL 3 samplers are actual objects, separate
from textures. It makes sense to do this already as it also
cleans up code organization quite a bit.

Userland/Libraries/LibGL/Tex/Sampler2D.cpp

@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2021, Stephan Unverwerth <s.unverwerth@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "Sampler2D.h"
+
+#include <LibGL/Tex/Texture2D.h>
+#include <math.h>
+
+namespace GL {
+
+static constexpr float wrap_repeat(float value)
+{
+    return value - floorf(value);
+}
+
+FloatVector4 Sampler2D::sample(FloatVector2 const& uv) const
+{
+    // FIXME: Calculate the correct mipmap level here, need to receive uv derivatives for that
+    unsigned lod = 0;
+
+    MipMap const& mip = m_texture.mipmap(lod);
+
+    float x = uv.x();
+    float y = uv.y();
+
+    switch (m_wrap_s_mode) {
+    case GL_REPEAT:
+        x = wrap_repeat(x);
+        break;
+
+    default:
+        VERIFY_NOT_REACHED();
+    }
+
+    switch (m_wrap_t_mode) {
+    case GL_REPEAT:
+        y = wrap_repeat(y);
+        break;
+
+    default:
+        VERIFY_NOT_REACHED();
+    }
+
+    x *= mip.width() - 1;
+    y *= mip.height() - 1;
+
+    return mip.texel(static_cast<unsigned>(x), static_cast<unsigned>(y));
+}
+
+}