[lib] Extract userSurfacedPermissionsFromRolePermissions

Summary:
This diff extracts a function from useRoleUserSurfacedPermissions, which I'm naming userSurfacedPermissionsFromRolePermissions.

We want to use this extracted function to address ENG-9031. It will be called by the keyserver from updateRoles to determine the currently-selected set of user-surfaced permissions.

Depends on D13068

Test Plan: This is a simple move diff. Besides Flow, it was also tested in combination with subsequent diffs

Reviewers: tomek, inka

Reviewed By: tomek

Differential Revision: https://phab.comm.dev/D13073