Add "sasl_protocol: oauthbearer" which does not add default handlers

[sverrehu]

Description

Using the existing sasl_protocol: oauth will add callback handlers for Confluent-provided classes. This PR adds a similar sasl_protocol: oauthbearer that will not automatically set up any callback handlers.

Fixes #1089

Type of change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

How Has This Been Tested?

Molecule test, and test in our local cluster.

Test Configuration:

Checklist:

• [x ] My code follows the style guidelines of this project
• [ x] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ x] I have made corresponding changes to the documentation
• [ ] My changes generate no new warnings
• [ x] I have added tests that prove my fix is effective or that my feature works
• [ ] Any dependent changes have been merged and published in downstream modules
• [ ] Any variable changes have been validated to be backwards compatible

[cla-assistant[bot]]

All committers have signed the CLA.