Add writeBits back in and use the optimizer to utilize the list conversion

examples/acceptance_tests/117/aiken.toml

@@ -0,0 +1,2 @@
+name = "aiken-lang/acceptance_test_117"
+version = "0.0.0"

examples/acceptance_tests/117/lib/tests.ak

@@ -0,0 +1,17 @@
+use aiken/builtin.{write_bits}
+
+test bar() {
+  let x =
+    if True {
+      [0, 1, 2, 3]
+    } else {
+      [0, 1]
+    }
+
+  write_bits(#"f0", x, True) == #"ff"
+}
+
+test baz() {
+  let x = [0, 1, 2, 3]
+  write_bits(#"f0", x, True) == #"ff"
+}