git: openjdk/jdk-sandbox: json: correct members() mutability after switch to LHM; add more mutability test cases

[duke]

Changeset: db3a4a7e
Branch: json
Author:    Justin Lu <justin.lu at oracle.com>
Date:      2025-04-21 15:08:53 +0000
URL:       https://git.openjdk.org/jdk-sandbox/commit/db3a4a7e6f99604571e713c1462a315d865e7351

correct members() mutability after switch to LHM; add more mutability test cases

! src/java.base/share/classes/java/util/json/JsonArrayImpl.java
! src/java.base/share/classes/java/util/json/JsonObjectImpl.java
! test/jdk/java/util/json/TestJsonArray.java
! test/jdk/java/util/json/TestJsonObject.java