Clean up the airflow.contrib package

[mik-laj]

Formerly the core code was maintained by the original creators - Airbnb. The code that was in the contrib package was supported by the community. The project was passed to the Apache community and currently the entire code is maintained by the community, so now the division has no justification, and it is only due to historical reasons.

Currently, we will try to clean up this mess and move the relevant modules to another place.

We have the following files left to move.

• airflow/contrib/__init__.py
• airflow/contrib/utils/__init__.py
• airflow/contrib/utils/weekday.py (Move out weekday from airflow.contrib #9388)
• airflow/contrib/utils/sendgrid.py (Move out sendgrid email from airflow.contrib #9355)
• airflow/contrib/utils/log/task_handler_with_custom_formatter.py
• airflow/contrib/utils/log/__init__.py (Move modules in airflow.contrib.utils.log to airflow.utils.log #9395)

Each move should be carried out in a backward-compatible manner. If appropriate, we should add a note in UPDATING.md

The list is automatically generated using the following command:

grep  'This \(module\|package\) is deprecated.' -riL airflow/contrib/

This is the explanation of the parameters used on grep

     -L, --files-without-match
             each file processed.
     -R, -r, --recursive
             Recursively search subdirectories listed.
     -i, --ignore-case
             Perform case insensitive matching.

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[mik-laj]

@ipeluffo @zikun @potiuk @feluelle @turbaszek Thanks for cooperation on this ticket.