E2T Test platform component

Base project: https://gerrit.o-ran-sc.org/r/ric-plt/xapp-frame/pkg/xapp

General Description

E2T is a platform component stub which has following behaviors

• Receives, decodes and prints out the content of RMR messages
• Sends Subscription Response message (12011) to each RMR message using it's sub_id
• Sends Subscription Response with invalid subscription ID in every 14 second
• Sends Subscription Response with malformed payload in every 14 second
• Set E2T_RAWDATA to override default encoded payload (use hex dump format)