CI(benchmarking): Add Sharded Tenant for pgbench

[bayandin]

Problem

During Nightly Benchmarks, we want to collect pgbench results for sharded tenants as well.

CI runs:

• https://github.com/neondatabase/neon/actions/runs/8359992563/job/22884611579
• https://github.com/neondatabase/neon/actions/runs/8380758214

Summary of changes

• Add pre-created sharded project for pgbench

Checklist before requesting a review

• I have performed a self-review of my code.
• If it is a core feature, I have added thorough tests.
• Do we need to implement analytics? if so did you add the relevant metrics to the dashboard?
• If this PR requires public announcement, mark it with /release-notes label and add several sentences in this section.

Checklist before merging

• Do not forget to reformat commit message to not include the above checklist

[github-actions]

2748 tests run: 2609 passed, 0 failed, 139 skipped (full report)

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Code coverage* (full report)

• functions: 28.2% (6328 of 22474 functions)
• lines: 47.0% (44512 of 94720 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
0f172de at 2024-03-28T18:47:58.546Z :recycle:}