RFR: 7132279: (ch) SeekableByteChannel operation may throw Non{Readable,Writable}ChannelException

[Brian Burkhalter]

Fix the specifications of the `read` and `write` methods in `SeekableByteChannel` and `FileChannel` to indicate that a `NonReadableChannelException` or `NonWritableChannelException`, respectively.

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Commit messages:
 - 7132279: (ch) SeekableByteChannel operation may throw Non{Readable,Writable}ChannelException

Changes: https://git.openjdk.org/jdk/pull/11141/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11141&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-7132279
  Stats: 17 lines in 2 files changed: 8 ins; 9 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/11141.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11141/head:pull/11141

PR: https://git.openjdk.org/jdk/pull/11141