fix(jsi): resolve Symbol.dispose without JS eval (#3855)

JsiHostObject::get fell back to runtime.global().eval("Symbol.for('Symbol.dispose');")
for the dispose-symbol lookup on every property miss. With a Hermes build that
disables the JS eval builtin,
the first miss throws an uncaught jsi::JSError and crashes the app on boot —
reproducibly seen when Reanimated 4 worklets access `_isReanimatedSharedValue`
on a Skia HostObject during MapperRegistry setup.

Replace the eval invocation with a direct JSI traversal of `Symbol.for`. The
behaviour is equivalent (Symbol.for("Symbol.dispose") returns the same well-known
symbol regardless of how it is reached) and the path no longer depends on the JS
eval builtin being available.

Remove the now-unused `RNJsi::eval` helper (no other consumers in this file or
across the package).

Co-authored-by: William Candillon <wcandillon@gmail.com>

Author: kewdex

packages/skia/cpp/jsi/JsiHostObject.cpp

@@ -24,12 +24,6 @@ void JsiHostObject::set(jsi::Runtime &rt, const jsi::PropNameID &name,
   }
 }
 
-jsi::Value eval(jsi::Runtime &runtime, const std::string &js) {
-  return runtime.global()
-      .getPropertyAsFunction(runtime, "eval")
-      .call(runtime, js);
-}
-
 jsi::Value JsiHostObject::get(jsi::Runtime &runtime,
                               const jsi::PropNameID &name) {
   auto nameStr = name.utf8(runtime);
@@ -86,7 +80,11 @@ jsi::Value JsiHostObject::get(jsi::Runtime &runtime,
   // Check for dispose symbol as last resort
   static const auto disposeSymbol = jsi::PropNameID::forSymbol(
       runtime,
-      eval(runtime, "Symbol.for('Symbol.dispose');").getSymbol(runtime));
+     runtime.global()
+          .getPropertyAsObject(runtime, "Symbol")
+          .getPropertyAsFunction(runtime, "for")
+          .call(runtime, "Symbol.dispose")
+          .getSymbol(runtime));
   if (jsi::PropNameID::compare(runtime, disposeSymbol, name)) {
     // Recursively call get with "dispose" string
     auto disposeName = jsi::PropNameID::forAscii(runtime, "dispose");