Rename BPF_FS_PATH to BPF_TIMEINSTATE_PATH.

Since we need a new path here, let's also change the name to not be confusing.

Bug: 422976190

Test: Recorded a Perfetto trace with statsd atom CPU_CYCLES_PER_UID_CLUSTER.

Flag: EXEMPT refactor

Change-Id: Ia0a2e2f0c45080488a4d949d3c2953a8fac44bb5