Provide trace instrumentation for Cloud SQL

[lkleeven]

Is your feature request related to a problem? Please describe.
Cloud SQL offers traces and a way of connecting them to existing traces by using SQL comments. There is currently no way of doing this that works for any Java libraries except for Hibernate.

Describe the solution you'd like
Integration trace instrumentation support into spring-cloud-gcp Cloud SQL so this works out of the box. Just like this is being offered for Pub/Sub. Applying this on the datasource layer could provide a universal solution.

Describe alternatives you've considered
We've looked at sqlcommenter but this only works for Hibernate.

[rogierlommers]

Nice! Would love to have this implemented.