SwapsController persistence opperation delay

## What is this about?

Performance optimization for MetaMask's SwapsController and persistence operations that are causing significant delays in user interactions.

## Scenario

Users experience slow response times when:
- Opening token details (300-600ms delay)
- Any persistence operations, especially with multiple accounts (~300ms per operation)

The root causes are:
1. `fetchTokenWithCache` function in SwapsController taking 300-600ms, primarily due to `immer` overhead in `this.update` calls
2. Slow persistence operations caused by processing the large `engine` field from state

## Design

NA

## Technical Details

**Current Issues:**
- `@metamask/swaps-controller/dist/SwapsController.js:425` - `fetchTokenWithCache` function performance bottleneck
- `immer` processing in `this.update` consuming majority of execution time
- Persistence operations scaling poorly with account count due to `engine` field processing

**Proposed Solutions:**
1. **SwapsController Optimization:**
- Implement selective state updates to avoid full `immer` processing
- Cache token data more efficiently to reduce redundant API calls
- Consider lazy loading or background fetching strategies

2. **Persistence Optimization:**
- Exclude or minimize `engine` field processing during persistence
- Implement incremental state persistence
- Add state segmentation to avoid processing unnecessary data

3. **General Improvements:**
- Add performance monitoring to track improvements
- Implement batching for multiple rapid state changes
- Consider using more efficient state management patterns for frequently updated data

## Threat Modeling Framework

- **Availability:** Performance issues affect user experience and app responsiveness
- **Integrity:** Ensure optimizations don't compromise data consistency
- **Confidentiality:** No security implications expected from performance improvements

## Acceptance Criteria

- [ ] `fetchTokenWithCache` execution time reduced to <100ms
- [ ] Persistence operations complete in <100ms regardless of account count
- [ ] Token detail opening feels instantaneous to users
- [ ] All existing functionality remains intact
- [ ] Performance improvements verified through automated tests
- [ ] No regressions in swap functionality
- [ ] Memory usage doesn't increase significantly

## Stakeholder review needed before the work gets merged

- [x] Engineering (needed in most cases)
- [ ] Design
- [x] Product
- [x] 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

- SwapsController source: `@metamask/swaps-controller/dist/SwapsController.js:425`
- Related to token detail view performance
- Immer documentation for optimization strategies
- Performance profiling data showing 300-600ms delays

Start by profiling fetchTokenWithCache in @metamask/swaps-controller/dist/SwapsController.js:425 and reviewing the reported Immer and persistence delays. Compare the results against the proposed persistence and state-update areas, then verify the acceptance criteria with automated performance and swap regression tests.

Written by the indexing model from the issue text.