RightAssignmentInitializer needs a performance improvement

When running the refresh-db profile on Malawi data, that has 300 users and 900 facilities, the generation of permission strings takes about an hour. We should improve this - if we want to reuse this profile in the future it should perform better for this volume of data (which is not that big).

Note: after the right assignments are created (about 110k of them) Javers goes through all of them and updates their history. (another hour). See OLMIS-3078. Do we need Javers for this entity?

Data is approximately:

• 300 users

• 900 facilities

• avg 15 role assignments per user

• each supervision role assignment is 20-80 supervised facilities

Acceptance criteria:

• Refresh db for the data like above takes a more reasonable time (less than 10 minutes)