[lworld] RFR: 8375499: [lworld] IR framework tests fail with UseAltSubstitutabilityMethod

[Tobias Hartmann]

TestLWorld.java and TestLWorldProfiling.java fail if `-XX:+UseAltSubstitutabilityMethod` is the default because they expect the substitutability test method to be named "isSubstitutable" and not "isSubstitutableAlt".

Thanks,
Tobias

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Commit messages:
 - JDK-8375499

Changes: https://git.openjdk.org/valhalla/pull/1919/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1919&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8375499
  Stats: 49 lines in 2 files changed: 0 ins; 0 del; 49 mod
  Patch: https://git.openjdk.org/valhalla/pull/1919.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1919/head:pull/1919

PR: https://git.openjdk.org/valhalla/pull/1919