fix: Allow passing in a custom wait strategy string in MySQL, Cassandra, Kafka and Trino (#953)

Hey,

Just a small change in adding the ability to pass in a custom wait
strategy message for MySQL. The current implementation had '.*: ready
for connections.*: ready for connections.*' as a default regex with no
option to change it. This PR moves it into a parameter.
No new functionality has been added so I presume the tests can stay the
same.

If you find this useful, I can also go over the other implementations
and make a similar change wherever this is a problem.