Refactor Reach repository layout

[SamDepardieu]

Description

This PR aims to simplify the folder architecture in Reach.

• Remove old reach folder
• Put pipeline tasks in a pipeline folder`
• Put Reach web application at the root in a web folder
• Remove old airflow related architecture and replace it by current architecture

Type of change

• [x] :fire: Breaking change

How Has This Been Tested?

make docker-test