refactor: update persistence module to TS

[jaissica12]

Background

• Continuing the effort to migrate remaining JavaScript modules to TypeScript for improved type safety and developer experience across the SDK codebase.

What Has Changed

• Converted src/persistence.js to src/persistence.ts with full type annotations on all methods, parameters, and return types
• Updated src/persistence.interfaces.ts with corrected and expanded interface definitions to support the conversion
• Updated test/jest/persistence.spec.ts with type adjustments for the converted module

Screenshots/Video

• {Include any screenshots or video demonstrating the new feature or fix, if applicable}

Checklist

• I have performed a self-review of my own code.
• I have made corresponding changes to the documentation.
• I have added tests that prove my fix is effective or that my feature works.
• I have tested this locally.

Additional Notes

• {Any additional information or context relevant to this PR}

Reference Issue (For employees only. Ignore if you are an outside contributor)

• Closes https://go/j/SDKE-1107

[sonarqubecloud]

Quality Gate passed

Issues
42 New issues
0 Accepted issues

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

See analysis details on SonarQube Cloud