RFR: 8302144: Move ZeroTLABTest.java to tier3

Fri Feb 17 16:50:50 UTC 2023

This is a "Hello World" test for the flags `UseTLAB` and `ZeroTLAB`, running with `-Xcomp`. It takes about 30seconds.
This test does not need to run on `tier1`. So I pushed it out to `tier3`.

Moved it to tier3, by adding it to hotspot_slow_compiler, which is excluded from tier1 and tier2.

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Commit messages:
 - 8302144: Move ZeroTLABTest.java to tier3

Changes: https://git.openjdk.org/jdk/pull/12620/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12620&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8302144
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/12620.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12620/head:pull/12620

PR: https://git.openjdk.org/jdk/pull/12620