[AETHER-1230] Prevents the ejection of the P4RuntimePacketProvider listener

Offloads to a predictable executor the handling of the packet-ins.
Without this the listener can be easily ejected as its execution includes
the PacketProviderService and potentially all the processors installed by the apps
and everything is executed in the context of the core dispatcher thread

Change-Id: I2e5f57fdf0a0a21a8f4f3c8326e4268467328833
(cherry picked from commit 283e217508b46d002f9e4640ea62cd7a63334a8c)
diff --git a/providers/p4runtime/packet/src/main/java/org/onosproject/provider/p4runtime/packet/impl/OsgiPropertyConstants.java b/providers/p4runtime/packet/src/main/java/org/onosproject/provider/p4runtime/packet/impl/OsgiPropertyConstants.java
new file mode 100644
index 0000000..9dadb40
--- /dev/null
+++ b/providers/p4runtime/packet/src/main/java/org/onosproject/provider/p4runtime/packet/impl/OsgiPropertyConstants.java
@@ -0,0 +1,30 @@
+/*
+ * Copyright 2021-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.provider.p4runtime.packet.impl;
+
+/**
+ * Constants for default values of configurable properties.
+ */
+public final class OsgiPropertyConstants {
+
+    private OsgiPropertyConstants() {}
+
+    public static final String P4RUNTIME_PACKET_PROVIDER_WORKERS = "workers";
+
+    public static final int P4RUNTIME_PACKET_PROVIDER_WORKERS_DEFAULT = 4;
+
+}