RFR: 8371689: (fs) CopyMoveHelper.copyToForeignTarget use of sourcePosixView is confusing

[Brian Burkhalter]

In `CopyMoveHelper`, replace `PosixFileAttributeView` with a `boolean`.

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Commit messages:
 - 8371689: (fs) CopyMoveHelper.copyToForeignTarget use of sourcePosixView is confusing

Changes: https://git.openjdk.org/jdk/pull/28304/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28304&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8371689
  Stats: 12 lines in 1 file changed: 4 ins; 2 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/28304.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28304/head:pull/28304

PR: https://git.openjdk.org/jdk/pull/28304