RFR: 8313676: Amend TestLoadIndexedMismatch test to target intrinsic directly

[Aleksey Shipilev]

See the bug for the reasons. Basically, we want to target the intrinsic directly, to avoid the dependence on the JDK code shape.

Additional testing:
 - [x] mainline: test is still sensitive to JDK-8313402 fix
 - [x] 17u: test is _now_ sensitive to JDK-8313402 fix

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jdk/pull/15136/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15136&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8313676
  Stats: 7 lines in 2 files changed: 5 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/15136.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15136/head:pull/15136

PR: https://git.openjdk.org/jdk/pull/15136