internal/shader: add tests for arrays

internal/shader/testdata/array3.expected.vs

@@ -0,0 +1,13 @@
+void F0(void);
+
+void F0(void) {
+	float l0[2];
+	l0[0] = float(0);
+	l0[1] = float(0);
+	float l1[2];
+	l1[0] = float(0);
+	l1[1] = float(0);
+	(l0)[0] = 1.0;
+	l1[0] = l0[0];
+	l1[1] = l0[1];
+}

internal/shader/testdata/array3.go

@@ -0,0 +1,7 @@
+package main
+
+func Foo() {
+	a := [2]float{1}
+	_ = a
+	return
+}