Matomo: Support the disabling of cookies

What does this MR do?

Incorporates community contribution (#271263 (closed), !45905 (closed)) by @otheus.uibk.

Relevant Matomo docs:

• How do I disable all cookies for a visitor?
• What are the cookies created by matomo javascript tracking client?

Piwik was previously renamed to Matomo (!45658 (merged)).

Couldn't find any documentation here related to Matomo. But there is a page describing settings in the helm chart docs, so that can be updated with the helm MR.

Related MRs

Omnibus MR: omnibus-gitlab!4979 (merged)

Helm chart MR: gitlab-org/charts/gitlab!1813 (merged)

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