feat: Add ZRTL iterator protocol, test harness, and derive macros

SDK enhancements:
- Add iterator protocol to zrtl.h (ZrtlIterator, ZrtlArrayIterator, ZrtlStringIterator)
- Add UTF-8 codepoint iteration for strings
- Add ZrtlIterableVtable for custom iterable types
- Add test harness macros (ZRTL_TEST, ZRTL_ASSERT_*, ZRTL_TEST_MAIN)

zrtl_macros improvements:
- Add #[derive(ZrtlType)] for implementing ZrtlTyped trait
- Support #[zrtl(name = "...", category = "...")] attributes
- Change type references to use ::zrtl:: namespace
- Update license to Apache-2.0 for consistency

reflaxe runtime:
- Rename crate from haxe_zyntax_runtime to reflaxe_haxe_runtime

Author: darmie

reflaxe.zyntax/runtime/Cargo.toml

@@ -1,9 +1,10 @@
 [package]
-name = "haxe_zyntax_runtime"
+name = "reflaxe_haxe_runtime"
 version = "0.1.0"
 edition = "2021"
 
-# It belongs to the Haxe frontend implementation
+# It belongs to the Haxe frontend implementation (reflaxe.zyntax)
+# Contains Haxe String, Array, Map, and other data structure implementations
 
 [lib]
 crate-type = ["cdylib", "rlib"]