Drop using BNG attachment IDs in favor or dynamically allocated line IDs

The current implementation of BngProgrammable for fabric.p4 uses
attachment IDs as line IDs, thus forcing apps such as bngc to be aware
of such implementation detail and to manage the allocation of such IDs.
Unfortunately, allocation of IDs is dependent on the device (P4 program)
implementation (e.g., line counter size), and so it should not be left
to apps.

This patch removes the need for attachment IDs at all and instead relies
on a driver-level service to dynamically allocate line IDs based on the
attachment attributes (currently s-tag, c-tag, mac address).

The current implementation of the allocation logic is a trivial one,
i.e. non-distributed and non-optimized.

Change-Id: Ie960936ee750cf565b8de41370085ecf9d49e931
diff --git a/pipelines/fabric/impl/src/test/java/org/onosproject/pipelines/fabric/impl/behaviour/bng/FabricBngLineIdAllocatorHandleTest.java b/pipelines/fabric/impl/src/test/java/org/onosproject/pipelines/fabric/impl/behaviour/bng/FabricBngLineIdAllocatorHandleTest.java
new file mode 100644
index 0000000..bff0b24
--- /dev/null
+++ b/pipelines/fabric/impl/src/test/java/org/onosproject/pipelines/fabric/impl/behaviour/bng/FabricBngLineIdAllocatorHandleTest.java
@@ -0,0 +1,41 @@
+/*
+ * Copyright 2019-present Open Networking Foundation
+ *
+ * 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 org.onosproject.pipelines.fabric.impl.behaviour.bng;
+
+import com.google.common.testing.EqualsTester;
+import org.junit.Test;
+
+/**
+ * Tests for FabricBngLineIdAllocator.Handle.
+ */
+public class FabricBngLineIdAllocatorHandleTest {
+
+    @Test
+    public void equalityTest() {
+        var handle1 = new FabricBngLineIdAllocator.Handle(
+                new MockAttachment(1));
+        var sameAsHandle1 = new FabricBngLineIdAllocator.Handle(
+                new MockAttachment(1));
+        var handle2 = new FabricBngLineIdAllocator.Handle(
+                new MockAttachment(2));
+
+        new EqualsTester()
+                .addEqualityGroup(handle1, sameAsHandle1)
+                .addEqualityGroup(handle2)
+                .testEquals();
+    }
+}
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