Add Patroni to GitLab component list

What does this MR do?

Add documentation for Patroni to the GitLab documentation page.

Todo

• An overview of the role of Patroni
• The benefits of using Patroni
• Considerations for using Patroni (e.g. a note about the benefits of keeping GitLab deployments simple, as described in https://docs.gitlab.com/ee/administration/reference_architectures/)
• A link to the Patroni source page
• A note that Patroni is an optional alternative (but eventual replacement) to repmgr
• A link to configuration docs for Omnibus and the charts

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Closes: omnibus-gitlab#5602 (closed)