Investigate on Firefox CPU/loading issues

### What is this about?

Based on logs shared by [this user](https://github.com/MetaMask/metamask-extension/issues/34428#issuecomment-4031966605), there are some CPU/loading issues on Firefox.

Preliminary analysis raises the following possible root causes:
- **High number of connections/listeners**: There are 98 MaxListenersExceededWarning entries in the logs, which suggests either many connections (e.g. many tabs open) or something adding listeners / creating streams without cleaning up.
- **ExtensionStore slowness**: There are several large write times (1924ms, 847ms, 6536ms, 1637ms, 716ms, and many in the 800–900ms range).
- **Fetch failures (NetworkError)**: These may be related to loading source map.

We should investigate what can be done to solve these issues.

### Scenario

_No response_

### Design

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### Technical Details

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### Threat Modeling Framework

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### Acceptance Criteria

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### Stakeholder review needed before the work gets merged

- [x] Engineering (needed in most cases)
- [ ] Design
- [ ] Product
- [ ] QA (automation tests are required to pass before merging PRs but not all changes are covered by automation tests - please review if QA is needed beyond automation tests)
- [ ] Security
- [ ] Legal
- [ ] Marketing
- [ ] Management (please specify)
- [ ] Other (please specify)

### References

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