[lworld] RFR: 8361166: [lworld] TestG1BarrierGeneration still fails after JDK-8343420

[Damon Fenacci]

The `TestG1BarrierGeneration::testArrayStore` and `TestG1BarrierGeneration::testArrayStoreTwice` tests are failing with `-XX:-TieredCompilation` because the compilation is inserting a `CastPP` node for the input of the `StoreP` node and this is restricting the type of the barrier to `notnull`. The test regex checks for exactly `pre post` (nothing after that) and thus fails.
This change fixes the test IR rules by restricting the current ones to `-XX:+TieredCompilation` and checking for `pre post notnull` for the `-XX:-TieredCompilation` case.

Tests: Tier 1-3+

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Commit messages:
 - JDK-8361166: [lworld] TestG1BarrierGeneration still fails after JDK-8343420

Changes: https://git.openjdk.org/valhalla/pull/1502/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1502&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8361166
  Stats: 17 lines in 2 files changed: 12 ins; 1 del; 4 mod
  Patch: https://git.openjdk.org/valhalla/pull/1502.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1502/head:pull/1502

PR: https://git.openjdk.org/valhalla/pull/1502