Enable serialization for BackendSimulator

[esantorella]

Summary: Context: For benchmarking, we would like to be able to store a BackendSimulator and reload and inspect it later. So it needs to be serializable.

This PR:

• Enable serialization and deserialization for BackendSimulator and the dataclasses it depends on, SimTrial and BackendSimulatorOptions
• Adds a test stub which is then used in multiple tests, including one for serialization

Differential Revision: D66102399

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D66102399

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D66102399

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 95.70%. Comparing base (0cab5d2) to head (aaa03cf).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #3077 +/- ## ======================================= Coverage 95.70% 95.70% ======================================= Files 487 488 +1 Lines 49525 49529 +4 ======================================= + Hits 47396 47400 +4 Misses 2129 2129 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

---

🚨 Try these New Features:

• Flaky Tests Detection - Detect and resolve failed and flaky tests
• JS Bundle Analysis - Avoid shipping oversized bundles

[facebook-github-bot]

This pull request has been merged in facebook/Ax@b9acb795e683d3759553082c2de662f927c2eb80.