Protocomm : Added component core for protocol communication

* This manages secure sessions and provides framework for multiple transports.
* The application can use protocomm layer directly to have application specific extensions for provisioning (or non-provisioning) use cases.
* Following features are available for provisioning :

  * Security - Security0 (no security), Security1 (curve25519 key exchange + AES-CTR encryption)
  * Proof-of-possession support for Security1

* Protocomm requires specific protocol buffer modules for compilation which can be generated from the `.proto` files in the `proto` directory using make.

Co-Authored-By: Amey Inamdar <amey@espressif.com>
Co-Authored-By: Anurag Kar <anurag.kar@espressif.com>

components/protocomm/proto/session.proto

@@ -0,0 +1,21 @@
+syntax = "proto3";
+
+import "sec0.proto";
+import "sec1.proto";
+
+/* Allowed values for the type of security
+ * being used in a protocomm session */
+enum SecSchemeVersion {
+    SecScheme0 = 0; /*!< Unsecured - plaintext communication */
+    SecScheme1 = 1; /*!< Security scheme 1 - Curve25519 + AES-256-CTR*/
+}
+
+/* Data structure exchanged when establishing
+ * secure session between Host and Client */
+message SessionData {
+    SecSchemeVersion sec_ver = 2;   /*!< Type of security */
+    oneof proto {
+        Sec0Payload sec0 = 10;      /*!< Payload data in case of security 0 */
+        Sec1Payload sec1 = 11;      /*!< Payload data in case of security 1 */
+    }
+}