RFR: 8344118: C2 SuperWord: add VectorThroughputForIterationCount benchmark

[Emanuel Peter]

Took idea of benchmark from here https://github.com/openjdk/jdk/pull/14581

It will be important for the efforts in:
[JDK-8344085](https://bugs.openjdk.org/browse/JDK-8344085): C2 SuperWord: improve vectorization for small loop iteration count

I ran the plots for `byte, int, long`.
We have aligned/unaligned scenarios, and compute-bound vs memory-bound scenarios.

We can very clearly see the effect of vectorization, and that with increasing `size`, we get increasingly better performance. But we can also see the effect of pre/post loops: this creates the saw-tooth curve.

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**Results**

red: normal -> saw-tooth
green: randomized offsets -> more "smooth"

linux_x64
![linux_x64](https://github.com/user-attachments/assets/1e63b47f-16a6-4766-985d-9da4cad25505)

linux_aarch64
![linux_aarch64](https://github.com/user-attachments/assets/77e9a880-32eb-43f8-a84b-16f39c1c2a62)

macosx_x64
![macosx_x64](https://github.com/user-attachments/assets/ab730367-d684-475c-b96d-e1093f56e776)

macosx_aarch64
![macosx_aarch64](https://github.com/user-attachments/assets/551484f5-79c7-41ea-b54d-e038d8c7b048)

windows_x64
![windows_x64](https://github.com/user-attachments/assets/3801577f-ac53-48ce-9b46-a2c9f0a2ddfe)

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Commit messages:
 - whitespace
 - Merge branch 'master' into JDK-8344118-VectorThroughputForIterationCount-benchmark
 - Merge branch 'master' into JDK-8344118-VectorThroughputForIterationCount-benchmark
 - Merge branch 'master' into JDK-8344118-VectorThroughputForIterationCount-benchmark
 - Merge branch 'master' into JDK-8344118-VectorThroughputForIterationCount-benchmark
 - JDK-8344118

Changes: https://git.openjdk.org/jdk/pull/22070/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22070&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8344118
  Stats: 436 lines in 1 file changed: 436 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/22070.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22070/head:pull/22070

PR: https://git.openjdk.org/jdk/pull/22070