MSSQLTo operators to use OdbcHook instead of MsSqlHook

[RosterIn]

What happened:
#6850 introduced OdbcHook and deprecated MsSqlHook
due to the deprecation of pymssql package.

As a result operators that are relaying on types from the pymssql package like:
MSSQLToGCSOperator, MsSqlToHiveTransfer will not be functional.

What you expected to happen:

MsSQLTO* operators needs to be changed to work with OdbcHook
see discussion on #6850

[dinigo]

This issue is giving us some trouble too. I was about to fill a new issue when I found this old one

pymssql is being discontinued. And it's been for some time now.
Some operators conflict with this, since there's no support for pymssql in python3.8. So it is impossible to use any pymssql based operators and hooks in the python3.8 build.

Can we migrate this to the pyodbc library to manage MSSQL connections?

pymssql/pymssql#668

[juarezr]

Good news!

pymssql is not being discontinued anymore.
@termim just released a new version compatible with python3.8.

Now it's possible to deploy Airflow supporting MSSQL with python3.8.

I don't know if it's worth trying to replace pymssql by pyodbc anymore. Anyone knows what's better for the airflow case?

[dinigo]

Great! I see we still have the deprecation warning running. @potiuk do you think it can be removed now that the library pymssql is back to stay?

/home/airflow/.local/lib/python3.8/site-packages/airflow/providers/google/cloud/transfers/mssql_to_gcs.py:25: DeprecationWarning: This module is deprecated due to the discontinuation of the pymssql project.

[RosterIn]

Interesting not sure what happens next that more for the project guys to decide. Maybe something should go on the mailing list?

[ashb]

Closed by #11537 -- I don't know enough about pyodbc, if someone is more familiar with it, feel free to comment/re-open this.