Add endpoint-peering benchmark

[gpauloski]

Description

Adds a new endpoint-peering benchmark for measuring endpoint-to-endpoint operations.

Note: this has revealed some very inefficient parts of the endpoints, but I will probably make a simpler script in the proxystore repo for debugging that.

Fixes N/A

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update (no changes to the code)
• CI change (changes to CI workflows, packages, templates, etc.)

Testing

Added unit tests and ran the benchmark to test.

Pull Request Checklist

Please confirm the PR meets the following requirements.

• Code changes pass pre-commit (e.g., black, flake8, mypy, etc.).
• Tests have been added to show the fix is effective or that the new feature works.
• New and existing unit tests pass locally with the changes.
• Docs have been updated and reviewed if relevant.