RFR: 8344183: (zipfs) SecurityManager cleanup in the ZipFS area

[Eirik Bjørsnøs]

Please review this PR which cleans up SecurityManager-related code following JEP-486 integraion.

* `ZipFileSystem` is updated to not perform `AccessController::doPrivileged`
* `ZipFileSystemProvider` is updated to not perform `AccessController::doPrivileged`
*  The test `TestPosix` is updated to perform `AccessController.doPrivileged`

This change should be relatively straight-forward to review. Reviewers may want to look extra close at the exception-unwrapping code in `ZipFileSystem::initOwner` and `ZipFileSystem::initGroup`.

Testing: Tests in `test/jdk/jdk/nio/zipfs` run green locally.

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Commit messages:
 - Cleanup SM-dependent code in the ZipFs area

Changes: https://git.openjdk.org/jdk/pull/22101/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22101&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8344183
  Stats: 80 lines in 3 files changed: 3 ins; 53 del; 24 mod
  Patch: https://git.openjdk.org/jdk/pull/22101.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22101/head:pull/22101

PR: https://git.openjdk.org/jdk/pull/22101