RFR: 8303073: (bf) Temporarily reinstate private DirectByteBuffer(long, int) constructor

[Claes Redestad]

We have a dependency on the renaissance benchmark suite for performance regression testing, which in turn has a dependency on a version of Spark that calls a private constructor that was recently chaned. To facilitate ongoing regression testing we want to temporarily put back a constructor with the old signature.

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Commit messages:
 - (bf) Temporarily reinstate private DirectByteBuffer(long, int) constructor

Changes: https://git.openjdk.org/jdk/pull/12717/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12717&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8303073
  Stats: 6 lines in 1 file changed: 5 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/12717.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12717/head:pull/12717

PR: https://git.openjdk.org/jdk/pull/12717