RFR: 8303508: Vector.lane() gets wrong value on x86

[Jatin Bhateja]

Incorrectness happens because compiler absorbs casting IR chain during idealizations.
Sign extending the result of sub-word extraction operation.

Please refer to detailed discussion on https://github.com/openjdk/jdk/pull/13070#issuecomment-1479779537 

Best Regards,
Jatin

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Commit messages:
 - Removing redundant imports from test.
 - 8303508: Vector.lane() gets wrong value on x86

Changes: https://git.openjdk.org/jdk/pull/13152/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13152&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8303508
  Stats: 91 lines in 3 files changed: 87 ins; 3 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/13152.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13152/head:pull/13152

PR: https://git.openjdk.org/jdk/pull/13152