RFR: 8344549: Cleanup AccessController in sun.misc.Unsafe

[Roger Riggs]

Unwrap calls using doPrivileged in jdk.unsupported sun.misc.Unsafe.

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Commit messages:
 - simplify declaration of INSTANCE
 - 8344549: Cleanup AccessController in sun.misc.Unsafe

Changes: https://git.openjdk.org/jdk/pull/22242/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22242&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8344549
  Stats: 16 lines in 1 file changed: 0 ins; 12 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/22242.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22242/head:pull/22242

PR: https://git.openjdk.org/jdk/pull/22242