[Role Logic Move] Rename feature flag

We created the role_controller_in_system_server feature flag, then later
made it a fixed flag. However, it has been observed that the fixed
flag documentation shows the following warning:

    IMPORTANT: Modifying the type of an existing flag is not supported.
    For example, you cannot change a regular flag to a fixed read-only
    flag, or vice versa. If you need to change the flag type, the best
    practice is to create a new flag.

By renaming the flag, we're effectively removing the old flag and
creating a new one. This should mitigate any issues implied by the
above warning.

Fix: 313529525
Test: atest CtsRoleTestCases
Change-Id: Ibb3f76a45e647e374af73429e8f0e01a7013dfd0