RFR: 8233451: (fs) Files.newInputStream() cannot be used with character special files

[Brian Burkhalter]

Add `isOther` and `available` methods to `FileChannelImpl` and the interfaces to native code and use these in `ChannelInputStream` to work around cases where a wrapped `FileChannelImpl` is not really seekable.

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Commit messages:
 - 8233451: (fs) Files.newInputStream() cannot be used with character special files

Changes: https://git.openjdk.org/jdk/pull/21508/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21508&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8233451
  Stats: 204 lines in 11 files changed: 188 ins; 0 del; 16 mod
  Patch: https://git.openjdk.org/jdk/pull/21508.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21508/head:pull/21508

PR: https://git.openjdk.org/jdk/pull/21508