[lworld] RFR: 8261156: [lworld] Re-enable C1 testing after mainline issues are fixed

[Tobias Hartmann]

Explicitly set `TieredStopAtLevel=4` in `TestLWorldProfiling` to avoid hitting mainline bug [JDK-8261225](https://bugs.openjdk.java.net/browse/JDK-8261225) and allow re-enabling C1 testing in the CI. I've also removed an unused flag from the framework.

Best regards,
Tobias

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Commit messages:
 - Workaround
 - 8261156: [lworld] Re-enable C1 testing after mainline issues are fixed

Changes: https://git.openjdk.java.net/valhalla/pull/333/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=333&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8261156
  Stats: 13 lines in 2 files changed: 3 ins; 8 del; 2 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/333.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/333/head:pull/333

PR: https://git.openjdk.java.net/valhalla/pull/333