[jdk16] RFR: 8258955: (bf) slice(int, int) on view buffers fails to adjust index according to primitive size

[Chris Hegarty]

Scale the slice start index per carrier width, for views of direct byte buffers. This never worked correctly since being added in Java 13.

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Commit messages:
 - Fix direct buffer slice

Changes: https://git.openjdk.java.net/jdk16/pull/73/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk16&pr=73&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8258955
  Stats: 35 lines in 2 files changed: 31 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk16/pull/73.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk16 pull/73/head:pull/73

PR: https://git.openjdk.java.net/jdk16/pull/73