RFR: 8361715: (bf) Improve java/nio/Buffer/GetChars.java and migrate to JUnit

[Brett Okken]

junit for CharSequence behavior of CharBuffer covering different CharBuffer implementations in various states (offset, position, limit)

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Commit messages:
 - whitespace
 - move parameterized data creation into method
 - linux line endings and subSequence test
 - JDK-8361715: create junit for CharSequence behavior of CharBuffer

Changes: https://git.openjdk.org/jdk/pull/26282/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26282&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8361715
  Stats: 133 lines in 1 file changed: 133 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/26282.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26282/head:pull/26282

PR: https://git.openjdk.org/jdk/pull/26282