Remove uid rules computation in NPMS.

Instead of computing uid rules separately by potentially calling
into other system services, use blocked reasons to derive the
uid rules for informing the listeners. Once we migrate the clients
to use NetworkPolicyCallback, we can remove uid rules entirely.

Bug: 202065802
Test: atest tests/cts/hostside/src/com/android/cts/net/HostsideRestrictBackgroundNetworkTests.java
Test: atest services/tests/servicestests/src/com/android/server/net/NetworkPolicyManagerServiceTest.java
Change-Id: Ifc3708c16ae7cf4d7ff26eac0ba1c6fbeb7ed7d9
Merged-In: Ifc3708c16ae7cf4d7ff26eac0ba1c6fbeb7ed7d9