RFR: 8331011: [XWayland] TokenStorage fails under Security Manager

[Alexander Zvegintsev]

This fix adds missing doPrivileged calls in TokenStorage, which is used to help take screenshots in Wayland.

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Commit messages:
 - initial

Changes: https://git.openjdk.org/jdk/pull/18950/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18950&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8331011
  Stats: 46 lines in 1 file changed: 26 ins; 0 del; 20 mod
  Patch: https://git.openjdk.org/jdk/pull/18950.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18950/head:pull/18950

PR: https://git.openjdk.org/jdk/pull/18950