Block migrations on MySQL when using bad collations/encoding

### Apache Airflow version main (development) ### Operating System MacOS 11.6 ### Versions of Apache Airflow Providers _No response_ ### Deployment Virtualenv installation ### Deployment details _No response_ ### What happened Currently we happily attempt to migrate the database regardless of what collation and encoding is used. This can cause migrations to fail unexpectedly, and with MySQL's lack of DDL transactions can leave the database in a half-migrated broken state (see #18939 and https://github.com/apache/airflow/issues/18939#issuecomment-953395944). ### What you expected to happen We should identify when we have bad values for encoding/collation, block migrations from happening, and offer detailed instructions on how to fix it. ### How to reproduce Create a MySQL database without specifying the encoding/collation as documented in [Setting up a MySQL database](https://airflow.apache.org/docs/apache-airflow/stable/howto/set-up-database.html#setting-up-a-mysql-database). ### Anything else _No response_ ### Are you willing to submit PR? - [X] Yes I am willing to submit a PR! ### Code of Conduct - [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)