Test: EigenPod Unit Test Refactor

## Description
Refactor EigenPod unit tests for simplicity and clarity

### Action Items
- [ ] Update EigenPod unit tests per [testing standards doc](https://docs.google.com/document/d/107Wn4cVjSOTng1T72TWhhzswj1Afw4Dz7fUXQWqzLT0/edit)
- [ ] Update testing doc with potential invariants to monitor and integration test TODOs 