[lib] Move stripPermissionsFromMemberInfo out of ...-types.js file

Summary:
We're going to create some "higher order" utility functions using stripPermissionsFromMemberInfo, so figured it would make sense to pull out of types file and into its own utility file.

For context, we're going to want to mirror the utility files in special-roles.js where we can patch RawThreadInfo and RawThreadInfos all in one go. This will make the changes to rawThreadInfoFromServerThreadInfo and the client migrations easier.

Depends on D12755

Test Plan: This is just a move diff, unit tests still pass. Note: There's still a validator unit test that is expected to fail. Going to address that now that flow stuff is reolved.

Reviewers: ashoat, tomek

Reviewed By: ashoat

Differential Revision: https://phab.comm.dev/D12756