MySQL not using config.DatabaseName

[thestephenstanton]

Describe the Bug
When using MySQL, the database name does not look like it is used for anything. If you want to specify a different database for the migrations than the connection string points at, things will break. Actually if you put anything into this field, it actually doesn't look like anything at all happens.

Steps to Reproduce
Steps to reproduce the behavior:

driver, err := mysql.WithInstance(writer, &mysql.Config{
	DatabaseName: "anything",
})

Just set that to anything you want and nothing will actually happen

Expected Behavior
I would expect that the database name passed in would take priority over the one in the connection string (or if one wasn't provided in the connection string)

Migrate Version
v4.18.2

Loaded Source Drivers
file

Loaded Database Drivers
mysql

Go Version
go 1.23

Additional context

Here is a PR: #1238