feat: implement for-in loop syntax with iterate/iteratorValue protocol and break support

Add `for (variable in sequence)` syntax to the Wren language, introducing the `in` keyword token and compiler support for iterating over sequences using `iterate` and `iteratorValue` methods. Includes new benchmark files for Lua, Python, Ruby, and Wren, plus test cases covering single-expression bodies, block bodies, closures over loop variables, and break statements. Also fixes a missing POP() in CLOSE_UPVALUE and moves the while test file to a subdirectory.

test/for/close_over_loop_variable.wren

@@ -0,0 +1,11 @@
+var list = []
+
+for (i in [1, 2, 3]) {
+  list.add(fn IO.write(i))
+  //list.add(fn IO.write(i))
+}
+
+for (f in list) f.call
+// expect: 1
+// expect: 2
+// expect: 3

test/for/closure_in_body.wren

@@ -0,0 +1,11 @@
+var list = []
+
+for (i in [1, 2, 3]) {
+  var j = i + 1
+  list.add(fn IO.write(j))
+}
+
+for (f in list) f.call
+// expect: 2
+// expect: 3
+// expect: 4

test/for/for_in_syntax.wren

@@ -0,0 +1,20 @@
+// Single-expression body.
+for (i in [1, 2, 3]) IO.write(i)
+// expect: 1
+// expect: 2
+// expect: 3
+
+// Block body.
+for (i in [1, 2, 3]) {
+  IO.write(i)
+}
+// expect: 1
+// expect: 2
+// expect: 3
+
+// Newline after "for".
+for
+(i in [1, 2, 3]) IO.write(i)
+// expect: 1
+// expect: 2
+// expect: 3

test/for/only_evaluate_sequence_once.wren

@@ -0,0 +1,10 @@
+var f = fn {
+  IO.write("evaluate sequence")
+  return [1, 2, 3]
+}
+
+for (i in f.call) IO.write(i)
+// expect: evaluate sequence
+// expect: 1
+// expect: 2
+// expect: 3