maint(core) Upgrade to scala 2.13 and Akka 2.6.21 (Do Not Merge)

[amolnayak311]

Pull Request checklist

• [ ] The commit(s) message(s) follows the contribution guidelines ?
• [ ] Tests for the changes have been added (for bug fixes / features) ?
• [ ] Docs have been added / updated (for bug fixes / features) ?

Current behavior : TODO

New behavior :

TODO

BREAKING CHANGES

TODO