RFR: 8310902: (fc) FileChannel.transferXXX async close and interrupt issues

[Alan Bateman]

This change fixes a number of bugs with FileChannel.transferTo/transerFrom that arise when the source or target channel is closed, or the thread is interrupted, during the transfer. More specifically:

- The direct implementations operate on the raw file descriptor and don't prevent the target/source channel from being closed during the transfer. For this PR, the direct transferTo is limited to cases where the target is a FileChannel or SocketChannel. It could be extended to other SelChImpl implementations (SinkChannel, DatagramChannel) if needed, but they are less interesting at this time.

- The transferTo/transferFrom methods are specified to throw ClosedByInterruptException after closing both channels. This is implemented inconsistently, and leaves one channel open in several cases.

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Commit messages:
 - Update
 - Update
 - Initial commit

Changes: https://git.openjdk.org/jdk/pull/14656/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14656&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8310902
  Stats: 850 lines in 3 files changed: 662 ins; 84 del; 104 mod
  Patch: https://git.openjdk.org/jdk/pull/14656.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14656/head:pull/14656

PR: https://git.openjdk.org/jdk/pull/14656