MySQL Grafana Cloud Integration Module

[rgeyer]

This introduces a new pattern for Grafana Cloud integrations/connections modules. These will include only the highly opinionated configuration details, and may leave much of the discovery of targets to the end user (see the integrations README.md)

This also introduces an example MySQL module which intends to demonstrate the concept and provide a point of discussion.

[mattdurham]

Can you add a link to this in the root README.md?