[jdk19u] RFR: 8290705: StringConcat::validate_mem_flow asserts with "unexpected user: StoreI"

[Tobias Hartmann]

Backport of [JDK-8290705](https://bugs.openjdk.java.net/browse/JDK-8290705). Applies cleanly. Approval is pending.

Thanks,
Tobias

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Commit messages:
 - 8290705: StringConcat::validate_mem_flow asserts with "unexpected user: StoreI"

Changes: https://git.openjdk.org/jdk19u/pull/34/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk19u&pr=34&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8290705
  Stats: 122 lines in 3 files changed: 122 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk19u/pull/34.diff
  Fetch: git fetch https://git.openjdk.org/jdk19u pull/34/head:pull/34

PR: https://git.openjdk.org/jdk19u/pull/34