Update usage of allowlist/denylist in some method names/comments.

In a previous change (https://r.android.com/1394342), we did a mass update of whitelist->allowlist
and blacklist->denylist in network policy related code. Updating
some usages of those (like allowlisted to allowed) to make them
sound natural.

Test: atest services/tests/servicestests/src/com/android/server/net/NetworkPolicyManagerServiceTest.java
Test: atest services/tests/servicestests/src/com/android/server/NetworkManagementInternalTest.java
Test: atest hostsidetests/net/src/com/android/cts/net/HostsideRestrictBackgroundNetworkTests.java
Change-Id: I6d34b0bd3cdb64d5872874fd9378bfc962a24f8d