RFR: 8318683: compiler/c2/irTests/TestPhiDuplicatedConversion.java "Failed IR Rules (2) of Methods (2)"

[Jasmine Karthikeyan]

This patch should fix the testbug where F16 conversions were expected but were not supported by the CPU. Instead of checking for AVX, I now check for `f16c` or `avx512vl`, mirroring the logic in vm_version_x86:
https://github.com/openjdk/jdk/blob/ec1bf23d012f007c126cb472fcff146cf7f41b1a/src/hotspot/cpu/x86/vm_version_x86.hpp#L770-L772

I went with the approach of changing the logic in the IR annotation itself instead of the test requirements, as the majority of the IR tests in this file should complete correctly on other platforms. Tier 1 testing passes on my (linux x64) machine. Reviews would be appreciated!

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Commit messages:
 - Check f16 cpu features for x86

Changes: https://git.openjdk.org/jdk/pull/16378/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16378&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318683
  Stats: 3 lines in 2 files changed: 1 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/16378.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16378/head:pull/16378

PR: https://git.openjdk.org/jdk/pull/16378