fix: fixed incorrect result endpoint for signature coverage

[lwin-kyaw]

Explanation

Fixes signature coverage result endpoint.

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, highlighting breaking changes as necessary
• I've prepared draft pull requests for clients and consumer packages to resolve any breaking changes

---

Note

Routes coverage result polling to the correct transaction/signature endpoints and refactors polling to accept a configurable result URL with optional timeout/interval.

• Shield Controller (packages/shield-controller)
  • Backend (src/backend.ts):
    • Update checkCoverage and checkSignatureCoverage to pass specific result URLs: v1/transaction/coverage/result and v1/signature/coverage/result.
    • Refactor #getCoverageResult to accept a configs object with coverageResultUrl (required) and optional timeout/pollInterval; use provided URL instead of hardcoded path.
  • Changelog:
    • Add Fixed entry for incorrect signature coverage result endpoint.

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[lwin-kyaw]

@metamaskbot publish-preview