[jdk21u-dev] RFR: 8333099: Missing check for is_LoadVector in StoreNode::Identity

[Martin Doerr]

Clean backport of [JDK-8333099](https://bugs.openjdk.org/browse/JDK-8333099).

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Commit messages:
 - Backport 2ea365c94533a59865ab4c20ad8e1008072278da

Changes: https://git.openjdk.org/jdk21u-dev/pull/787/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=787&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8333099
  Stats: 64 lines in 2 files changed: 63 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/787.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/787/head:pull/787

PR: https://git.openjdk.org/jdk21u-dev/pull/787