[jdk25u-dev] RFR: 8365570: C2 fails assert(false) failed: Unexpected node in SuperWord truncation: CastII

[Vishal Chand]

Clean backport of [8365570](https://github.com/openjdk/jdk/commit/775f48de6129092d05650fec17dad171944e6d89) - C2 fails assert(false) failed: Unexpected node in SuperWord truncation: CastII

*  Fixes assert failure in superword truncation with CastII. Since casts specifically change the type of a node, they should not be truncated during vectorization to maintain type safety.

* Additional Testing:

- [x]  New regression test fails without the fix, passes with it.
- [x]  Linux x86_64 server fastebug compiler tests.

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Commit messages:
 - Backport 775f48de6129092d05650fec17dad171944e6d89

Changes: https://git.openjdk.org/jdk25u-dev/pull/269/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk25u-dev&pr=269&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8365570
  Stats: 33 lines in 2 files changed: 31 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk25u-dev/pull/269.diff
  Fetch: git fetch https://git.openjdk.org/jdk25u-dev.git pull/269/head:pull/269

PR: https://git.openjdk.org/jdk25u-dev/pull/269