Clean up replication dbs on exit

[jaydoane]

Overview

Implement delete_on_exit/1 and use it to delete replication dbs for tests which currently lack clean up. Replace existing on_exit calls with new function.

Testing recommendations

Before this PR, run mix test --trace test/replication_test.exs and then look at /all_dbs and notice all the dbs like random-test-db--576460750833332000--576460752303423488_src etc.

After deleting those test dbs, apply this PR and run the tests again: all replication dbs should have been cleaned up.

Related Issues or Pull Requests

Checklist

• Code is written and works correctly;
• Changes are covered by tests;
• Documentation reflects the changes;