fix: avoid NPE in trustedLookup on environments without IMPL_LOOKUP, for issue #4011

[wenshao]

Summary

• On Android the static initializer leaves JDKUtils.IMPL_LOOKUP null (the Unsafe-based access to MethodHandles.Lookup.IMPL_LOOKUP is intentionally gated to !ANDROID). trustedLookup(Class) then NPE'd at IMPL_LOOKUP.in(...), producing the user-visible "Attempt to invoke virtual method MethodHandles$Lookup.in(...) on a null object reference" when parsing Kotlin data classes via JSON.parseObject on Android 16 (API 36).
• JDKUtils.trustedLookup: short-circuit and return null when IMPL_LOOKUP is unavailable. Most existing callers already wrap usage in try/catch and fall back to reflection-based access, so a null Lookup is the cleanest signal.
• ObjectReaderCreator.lambdaSetter / createBuildFunctionLambda: handle the null lookup explicitly and return null so callers fall back to reflection instead of throwing JSONException(\"create fieldReader error\").

Fixes #4011.

Test plan

• Existing JDKUtilsTest (uses trustedLookup with non-null IMPL_LOOKUP) still passes.
• ObjectReaderCreator*Test*, LambdaSetterTest* — all 38 tests pass.
• Verified on Android (would need an Android device run; reproducer in issue body).

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