Split parcelable .aidl files to aidl-export

The one-line "parcelable X" files need to be imported by targets that do
not build against SDK (the SDK has prebuilt definitions), so prepare a
dedicated directory for them.
This avoids having users of the classes include the whole src/
directory, which could contain definitions for classes that are not part
of the public API, so should not be imported.

Also move back to frameworks/base/core some .aidl definitions that
were separated from their associated class.

Bug: 171540887
Test: m
Merged-In: I7432fe4c87cd3cab04dcb6185c9a4f3f84376549
Change-Id: I7432fe4c87cd3cab04dcb6185c9a4f3f84376549

framework/src/android/net/apf/ApfCapabilities.aidl

@@ -1,20 +0,0 @@
-/*
-**
-** Copyright (C) 2019 The Android Open Source Project
-**
-** Licensed under the Apache License, Version 2.0 (the "License");
-** you may not use this file except in compliance with the License.
-** You may obtain a copy of the License at
-**
-**     http://www.apache.org/licenses/LICENSE-2.0
-**
-** Unless required by applicable law or agreed to in writing, software
-** distributed under the License is distributed on an "AS IS" BASIS,
-** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-** See the License for the specific language governing permissions and
-** limitations under the License.
-*/
-
-package android.net.apf;
-
-@JavaOnlyStableParcelable parcelable ApfCapabilities;