Switch previous and new code path in setUidRule

setUidRule was updated to use Java BpfMap class instead of native JNI
functions in aosp/2145583.
But it is better to verify this refactoring by the experiment.
So this commit update setUidRule to switch previous code path(JNI)
and new code path(Java) based on the flag.

Also this commit removes @GuardedBy("sUidOwnerMap") from
native_setUidRule.
This was needed to avoid JNI and Java code modify the UidOwnerMap
concurrently when some API uses previous code path (JNI) and other APIs
use new code path (Java BpfMap class).
But, after this topic, it will not be needed because all the APIs will use JNI
"or" all the APIs will use Java BpfMap class to update UidOwnerMap.

Bug: 217624062
Test: atest BpfNetMapsTest
android.net.cts.ConnectivityManagerTest#testFirewallBlocking

Change-Id: I0d293c3eb89649c969f09578639dc4cb0233501b
1 file changed