Organize the daily WYS DAG

[tahaislam]

The current structure of pull_wys DAG has too many tasks done within pull_wys task which is implemented in wys_api.py which contains many long sql queries. It could be better to split the task pull_wys into smaller tasks and convert these sql queries into PostgreSQL functions. That should help identifying bugs faster and testing new modifications easier.

[gabrielwol]

When we reorganize this DAG, rather than pulling all the raw data in one task (currently around 2 hours to pull 700 locations), it would be cool to dynamically generate a task for each location pulled by the previous signs API call. Con: that's a lot of tasks.