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/break/in_for_loop.wren

@@ -0,0 +1,10 @@
+for (i in [1, 2, 3, 4, 5]) {
+  IO.write(i)
+  if (i > 2) break
+  IO.write(i)
+}
+// expect: 1
+// expect: 1
+// expect: 2
+// expect: 2
+// expect: 3