Adding ISTIO Envoy Filter for Airflow Webserver Authentication

We are adding ISTIO Envoy filter for airflow Authentication because out of the box password based authentication is causing huge bottleneck, along with those some web server configurations will also be added

Changes required

1. Using default authentication in airflow (No auth) to leverage ISTIO

2. Adding an Envoy filter targeting only airflow deployment, any request to airflow webserver will be hijacked by the side car proxy and this custom authentication filter will be executed. This filter will be doing the existing Basic Authentication only, we are are mounting Azure Keyvault in the ISTIO side car to fetch the airflow password to validate the one sent in the request headers

3. Adding the airflow webserver configurations