[lib] Introduce stripMemberPermissionsFromRawThreadInfos

Summary:
This is the migrationFunc that will be consumed by createUpdateDBOpsForThreadStoreThreadInfos for the client migrations.

Depends on D12779

Test Plan: Included basic unit test. Will also be tested as part of native and web migrations.

Reviewers: ashoat, tomek

Reviewed By: ashoat

Differential Revision: https://phab.comm.dev/D12788