chore(tron): improve account sync observability

[taran-a]

Explanation

Improve observability of account synchronization failures in the Tron snap: per-account fetch failures were silently discarded (Promise.allSettled + flatMap dropped rejections), and adapter-level degradations were invisible — Sentry showed nothing actionable.

• @metamask/snap-networks-utils: add SynchronizationError, formatAccountSyncFailures, and the AccountSyncFailure type. Failure details (account IDs + reasons) are embedded in the error message because snap_trackError only serializes name, message, stack, and cause.
• AccountsService: report per-account fetch failures in one SynchronizationError per sync run (each failure attributed to its account via the settled-results order); track batch save failures standalone (Failed to save assets / Failed to save transactions, with the original error as cause). Reporting is defensive — a failure while reporting is logged and swallowed, never breaking the sync flow.
• SnapAssetsAdapter: make previously silent degradations visible — unexpected account-info failures currently treated as "inactive account" (a transient 500/timeout zeroes balances), TRC20-fallback failures, and spot-price failures — each tracked with a context message and the original error as cause. No behavior changes.

All new failures with proper description.

Account sync with 5 accounts id and reasons

References

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
96.3% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud