ci: use the microbenchmarks-pool

[v1v]

What

From now on we will use the same CI workers for the benchmarking

[ghost]

💚 Build Succeeded

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Build stats

• Start Time: 2022-07-08T08:18:36.553+0000

• Duration: 48 min 26 sec

Test stats 🧪

Test	Results
Failed	0
Passed	3054
Skipped	36
Total	3090

💚 Flaky test report

Tests succeeded.

🤖 GitHub comments

To re-run your PR in the CI, just comment with:

• /test : Re-trigger the build.

• run benchmark tests : Run the benchmark tests.

• run jdk compatibility tests : Run the JDK Compatibility tests.

• run integration tests : Run the Agent Integration tests.

• run end-to-end tests : Run the APM-ITs.

• run windows tests : Build & tests on windows.

• run elasticsearch-ci/docs : Re-trigger the docs validation. (use unformatted text in the comment!)

[v1v]

@eyalkoren , I cherry-picked your changes from 6059312

[v1v]

/test

[v1v]

I assume these errors are unrelated to the nature of this change, since it ran the Benchmarks without any trouble

[jackshirazi]

I think that one has become a flaky test, I'll re-run and investigate if it stays