RFR: 8264744: (fs) Use file cloning in Linux version of Files::copy method [v11]

[Brian Burkhalter]

> Add file cloning to `java.nio.channels.FileChannel::transferTo` and `java.nio.file.Files.copy(Path,Path)`.

Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:

  8264744: Reinstate copy_file_range in Linux; remove vestiges of macOS clonefile

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Changes:
  - all: https://git.openjdk.org/jdk/pull/9486/files
  - new: https://git.openjdk.org/jdk/pull/9486/files/4260d000..2a98f0fe

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9486&range=10
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9486&range=09-10

  Stats: 192 lines in 8 files changed: 46 ins; 145 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/9486.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9486/head:pull/9486

PR: https://git.openjdk.org/jdk/pull/9486