Implement and test dbt-mysql 0.19.0

[dbeatty10]

Describe the feature

The first beta for dbt core 0.19.0 is available, so work to test the dbt-mysql adapter can begin.

Describe alternatives you've considered

An alternative is to not create a release for dbt-mysql 0.19.0. The benefit of this alternative would be requiring no work. The downside would be limiting the utility of the MySQL adapter if it doesn't progress along with dbt core.

Additional context

It is completely unknown how much time this will take.

Who will this benefit?

This will benefit anyone who uses dbt and continues to upgrade their version of dbt core.

Are you interested in contributing this feature?

I intend to implement this feature 😃