RFR: 8273507: Using TestNG for unit testing ChannelInputStream::transferTo

[Markus KARG]

Using TestNG makes it easier to maintain and extend the unit test of ChannelInputStream::transferTo.

This change was proposed by Brian Burkhalter @blbp and requested Alan Bateman @AlanBateman.

*Note: A further test addition (testing 2GB+ transfers) will be added by me in a subsequent PR using TestNG once *this* PR is merged. This will need a while due to personal scheduling, also the topics are not necessarily related, hence there are separate PRs.*

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Commit messages:
 - Migrated to TestNG

Changes: https://git.openjdk.java.net/jdk/pull/5421/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5421&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8273507
  Stats: 61 lines in 1 file changed: 10 ins; 32 del; 19 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5421.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5421/head:pull/5421

PR: https://git.openjdk.java.net/jdk/pull/5421