feat: add WrenResolveModuleFn callback and module name parameter to wrenInterpret for relative import resolution

This breaking API change introduces a new `WrenResolveModuleFn` callback in the configuration that allows the host to canonicalize import module names, enabling relative imports. The `wrenInterpret()` function now requires a `module` parameter to specify the module name for the code being interpreted. The `wrenInterpretInModule()` function is removed in favor of the updated `wrenInterpret()`. The `metaCompile` function now dynamically looks up the caller's module name instead of hardcoding "main". New test files `resolution.c`, `resolution.h`, and `resolution.wren` are added to verify resolver behavior including null default, NULL return error, string rewriting, shared module deduplication, and importer propagation.

src/optional/wren_opt_meta.c

@@ -14,9 +14,17 @@ void metaCompile(WrenVM* vm)
   bool printErrors = wrenGetSlotBool(vm, 3);
 
   // TODO: Allow passing in module?
-  ObjClosure* closure = wrenCompileSource(vm, "main", source,
-                                          isExpression, printErrors);
+  // Look up the module surrounding the callsite. This is brittle. The -2 walks
+  // up the callstack assuming that the meta module has one level of
+  // indirection before hitting the user's code. Any change to meta may require
+  // this constant to be tweaked.
+  ObjFiber* currentFiber = vm->fiber;
+  ObjFn* fn = currentFiber->frames[currentFiber->numFrames - 2].closure->fn;
+  ObjString* module = fn->module->name;
 
+  ObjClosure* closure = wrenCompileSource(vm, module->value, source,
+                                          isExpression, printErrors);
+  
   // Return the result. We can't use the public API for this since we have a
   // bare ObjClosure*.
   if (closure == NULL)