RFR: 8355512: Test compiler/vectorization/TestVectorZeroCount.java times out with -XX:TieredStopAtLevel=3 [v2]

[Jasmine Karthikeyan]

> Hi all,
> This is a small patch to TestVectorZeroCount to make it only execute when C2 is enabled, to fix a timeout with -XX:TieredStopAtLevel=3. This test takes a long time to finish without C2 because it iterates through all of the integers twice. Since the intention of the test is to stress the C2-specific `numberOfLeadingZeros` and `numberOfTrailingZeros` intrinsics, I think it makes sense to limit it to running with C2 only.
> 
> Reviews would be appreciated!

Jasmine Karthikeyan has updated the pull request incrementally with one additional commit since the last revision:

  Change requires to run test on Graal as well

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Changes:
  - all: https://git.openjdk.org/jdk/pull/25243/files
  - new: https://git.openjdk.org/jdk/pull/25243/files/a35fbef4..3a7031fd

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25243&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25243&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/25243.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25243/head:pull/25243

PR: https://git.openjdk.org/jdk/pull/25243