[PT-5027] Add ruby 3.0 and 3.1 test matrix support

[pablomg92z]

Description

See https://catawiki.atlassian.net/browse/PT-5027.

This PR adds circleCI tests for ruby 2.7, 3.0 and 3.1, both unit tests and functional tests against a kafka docker image that has the same version as the one we use in production. However, the provider of the image is wurstmeister instead of confluent which is the one we use in production. The reasons for this are:

• wurstmeister image was the one already used with the library, so we didn't make any changes there
• Errors are connection errors which appear related to the configs in the images and not related to these changes
• The main goal of this PR is to have a test suite running that ensure that no breaking changes are made

Type of change

• Bug fix (non-breaking change which fixes an issue)

How has this been tested?

• CircleCI Unit and functional tests.

Checklist

• My changes generate no new warnings
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have checked my code and corrected any misspellings

Deployment notes

We need to generate a new gem release. The only code change is related to datadog, which we do not use, so there should be no functionality changes or issues upgrading to this version.

[muripic]

🚀

[muripic]

Please add in the description that we did not fix the errors and go for the change to the Confluent image in this PR because:

• wurstmeister image was the one already used with the library, so we didn't make any changes there
• Errors are connection errors which appear related to the configs in the images and not related to these changes
• The main goal of this PR is to have a test suite running that ensure that no breaking changes are made

[pablomg92z]

Please add in the description that we did not fix the errors and go for the change to the Confluent image in this PR because:

• wurstmeister image was the one already used with the library, so we didn't make any changes there
• Errors are connection errors which appear related to the configs in the images and not related to these changes
• The main goal of this PR is to have a test suite running that ensure that no breaking changes are made

done!