RFR: 8264744: (fs) Use file cloning in Linux and macOS versions of FileChannel transfer and Files copy methods [v6]

[Brian Burkhalter]

On Wed, 10 Aug 2022 01:05:06 GMT, Brian Burkhalter <bpb at openjdk.org> wrote:

>> Add file cloning to `java.nio.channels.FileChannel::transferTo` and `java.nio.file.Files.copy(Path,Path)`.
>
> Brian Burkhalter has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains eight commits:
> 
>  - 8264744: Remove CloneFile classes; refactor to use {Bsd,Linux}CopyFile
>  - Merge
>  - 8264744: Fix typo desintation -> destination
>  - 8264744: Refactor into UnixCopyFile hierarchy
>  - Merge
>  - 8264744: Address review comments aside from refactoring
>  - 8264744: Refactor into provider+dispatcher to reduce amount of JNI code
>  - 8264744: (fc, fs) Support file cloning in Unix versions of FileChannel transfer and Files copy methods

`clone()` moved to `{Bsd,Linux,Unix}FileSystem`; `{Bsd,Linux}CopyFile` removed.

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