ONOS-7066 ONOS-7067 PI abstractions refactoring and P4Info model parser

Includes changes previously reviewed in #15607, #15877, and #15955.

Change-Id: Ie2ff62e415f2099832ebfe05961a879b7b188fc3
diff --git a/core/api/src/main/java/org/onosproject/net/pi/model/PiMeterModel.java b/core/api/src/main/java/org/onosproject/net/pi/model/PiMeterModel.java
new file mode 100644
index 0000000..237da05
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/pi/model/PiMeterModel.java
@@ -0,0 +1,76 @@
+/*
+ * Copyright 2017-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.net.pi.model;
+
+import com.google.common.annotations.Beta;
+
+/**
+ * Model of a meter in a protocol-independent pipeline.
+ */
+@Beta
+public interface PiMeterModel {
+
+    /**
+     * Meter rate unit.
+     */
+    enum Unit {
+        /**
+         * Measures rate of bytes.
+         */
+        BYTES,
+        /**
+         * Measures rate of packets.
+         */
+        PACKETS
+    }
+
+    /**
+     * Returns the ID of this meter.
+     *
+     * @return meter ID
+     */
+    PiMeterId id();
+
+    /**
+     * Returns the type of this meter.
+     *
+     * @return meter type
+     */
+    PiMeterType meterType();
+
+    /**
+     * Returns the unit of this meter.
+     *
+     * @return unit
+     */
+    Unit unit();
+
+    /**
+     * Returns the table model associated with this meter. Meaningful only if the meter type is {@link
+     * PiMeterType#DIRECT}.
+     *
+     * @return table model
+     */
+    PiTableId table();
+
+    /**
+     * Returns the number of cells of this meter. Meaningful only if the meter type is {@link PiMeterType#INDIRECT}.
+     *
+     * @return size
+     */
+    long size();
+}